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WPF: How to assign IsMouseOver and IsPressed Button State backgrounds from Code Behind no XAML

I have some runtime generated WPF buttons that I need to style using code behind. I have the Style below in a code behind variable ( Style Editstyle = Application.Current.Resources[x] as Style;)
How would I change the DynamicResource of the values in the Trigger section from codebehind?
Like style.Trigger.IsFocused.Background = bitmapX;
Also style.Key="NewStyleCopy1";
<Style x:Key="INIT_A" TargetType="Button">
<Setter Property="FocusVisualStyle" Value="{x:Null}" />
<Setter Property="Background" Value="{DynamicResource back}" />
<Setter Property="Foreground" Value="{DynamicResource fore}" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Button">
<Border Name="border"
BorderBrush="{DynamicResource stroke}"
BorderThickness="1"
Padding="4,2"
CornerRadius="0"
Background="{TemplateBinding Background}">
<Grid>
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center" Name="content" />
</Grid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsFocused" Value="True">
<Setter Property="Background" Value="{DynamicResource altback}" />
<Setter Property="Foreground" Value="{DynamicResource altfore}" />
<Setter TargetName="border" Property="BorderBrush" Value="{DynamicResource altstroke}" />
<Setter Property="Button.Effect" Value="{DynamicResource a_hbtnglow}" />
</Trigger>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" Value="{DynamicResource altback}" />
<Setter Property="Foreground" Value="{DynamicResource altfore}" />
<Setter TargetName="border" Property="BorderBrush" Value="{DynamicResource altstroke}" />
<Setter Property="Button.Effect" Value="{DynamicResource a_hbtnglow}" />
</Trigger>
<Trigger Property="IsPressed" Value="True">
<Setter Property="Background" Value="{DynamicResource altback}" />
<Setter Property="Foreground" Value="{DynamicResource altfore}" />
<Setter TargetName="border" Property="BorderBrush" Value="{DynamicResource altstroke}" />
<Setter Property="Button.Effect" Value="{DynamicResource a_hbtnglow}" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

This is usually done in XAML by defining a Trigger for each state:
<Style TargetType="Button">
<Style.Triggers>
<Trigger Property="IsPressed" Value="True">
<Setter Property="Foreground" Value="Green" />
</Trigger>
</Style.Triggers>
</Style>
You can make use of the Style.BasedOn property to extend a particular Style, for example a default Style for all Button elements. This way you can create a more specific Style that includes all attributes of the base Style:
<Style x:Key="DefaultButtonStyle" TargetType="Button">
<Setter Property="Background" Value="Orange" />
</Style>
<Style x:Key="GeneratedButtonsStyle"
BasedOn="{StaticResource DefaultButtonStyle}"
TargetType="Button">
<!-- Override the base Style value -->
<Setter Property="Background" Value="Yellow" />
<!-- Extend the base Style -->
<Setter Property="Foreground" Value="Red" />
<Style.Triggers>
<Trigger Property="IsPressed" Value="True">
<Setter Property="Foreground" Value="Green"/>
</Trigger>
</Style.Triggers>
</Style>

I ended up copying the style and edited the properties.
I appreciate all your suggestions.
var xu = styleCopy("ButtonAA");
Trigger t = new Trigger();
t.Property = Button.IsMouseOverProperty;
t.Value = true;
Setter setter = new Setter();
setter.Property = Button.BackgroundProperty;
setter.Value = Brushes.Blue;
t.Setters.Add(setter);
xu.Triggers.Add(t);
btn.Style = xu;

Changing Foreground for IsMouseOver anf IsPressed is not working in custom style

No matter what I try I can't set get the trigger IsMouseOver and IsPressed to change the Foreground.
I have been trying to alter it in the Button itself.
<Button (STUFF HERE)>
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="Foreground" Value="#FF373737"/>
</Trigger>
<Trigger Property="IsPressed" Value="true">
<Setter Property="Foreground" Value="#FF4D4D4E"/>
</Trigger>
</Button>
I have been trying to look it up, but I am pretty amateur with XAML.

here the general layout for styling controls:
<Button Content="OK">
<Button.Style>
<Style TargetType="Button">
<Style.Triggers >
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="Foreground" Value="#FF373737"/>
</Trigger>
<Trigger Property="IsPressed" Value="true">
<Setter Property="Foreground" Value="#FF4D4D4E"/>
</Trigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
If you want to reuse the style, then save it to a resourcedictionary as a named style and you can refer to it on your controls

You have to create a style where you put the Triggers. Add this style to any resource dictionary in scope, e.g. the Window.Resources or the application resources if you want to reuse it across the application. If you omit the x:Key, you make it implicit and therefore apply to all Buttons in scope.
<Style x:Key="MyButtonStyle" TargetType="{x:Type Button}">
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Foreground" Value="#FF373737"/>
</Trigger>
<Trigger Property="IsPressed" Value="True">
<Setter Property="Foreground" Value="#FF4D4D4E"/>
</Trigger>
</Style.Triggers>
</Style>
Then reference that style in the Button.
<Button Style="{StaticResource MyButtonStyle}" .../>
Alternatively, you could also directly assign the style to the Button if it is the only one.
<Button Content="Styled">
<Button.Style>
<Style TargetType="{x:Type Button}">
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Foreground" Value="#FF373737"/>
</Trigger>
<Trigger Property="IsPressed" Value="True">
<Setter Property="Foreground" Value="#FF4D4D4E"/>
</Trigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
Note that while this works for the Foreground property, it does not for properties like Background as they are defined in the ControlTemplate triggers which take precedence over a style. In order change those, you have to copy and adapt the Button ControlTemplate.
Update for your comment. Maybe you understand the Foreground property wrong. It is used for the text color of the content, not the color of the button itself. The "blue-ish" tint is determined by the Background property and as stated above, you have to edit the ControlTemplate for that.
<Style x:Key="FocusVisual">
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate>
<Rectangle Margin="2" StrokeDashArray="1 2" SnapsToDevicePixels="true" StrokeThickness="1" Stroke="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<SolidColorBrush x:Key="Button.Static.Background" Color="#FFDDDDDD"/>
<SolidColorBrush x:Key="Button.Static.Border" Color="#FF707070"/>
<SolidColorBrush x:Key="Button.MouseOver.Background" Color="#FF373737"/>
<SolidColorBrush x:Key="Button.MouseOver.Border" Color="#FF3C7FB1"/>
<SolidColorBrush x:Key="Button.Pressed.Background" Color="#FF4D4D4E"/>
<SolidColorBrush x:Key="Button.Pressed.Border" Color="#FF2C628B"/>
<SolidColorBrush x:Key="Button.Disabled.Background" Color="#FFF4F4F4"/>
<SolidColorBrush x:Key="Button.Disabled.Border" Color="#FFADB2B5"/>
<SolidColorBrush x:Key="Button.Disabled.Foreground" Color="#FF838383"/>
<Style x:Key="ButtonStyle" TargetType="{x:Type Button}">
<Setter Property="FocusVisualStyle" Value="{StaticResource FocusVisual}"/>
<Setter Property="Background" Value="{StaticResource Button.Static.Background}"/>
<Setter Property="BorderBrush" Value="{StaticResource Button.Static.Border}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="HorizontalContentAlignment" Value="Center"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Padding" Value="1"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Border x:Name="border" Background="{TemplateBinding Background}" BorderThickness="{TemplateBinding BorderThickness}" BorderBrush="{TemplateBinding BorderBrush}" SnapsToDevicePixels="true">
<ContentPresenter x:Name="contentPresenter" Focusable="False" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsDefaulted" Value="true">
<Setter Property="BorderBrush" TargetName="border" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/>
</Trigger>
<Trigger Property="IsMouseOver" Value="true">
<Setter Property="Background" TargetName="border" Value="{StaticResource Button.MouseOver.Background}"/>
<Setter Property="BorderBrush" TargetName="border" Value="{StaticResource Button.MouseOver.Border}"/>
</Trigger>
<Trigger Property="IsPressed" Value="true">
<Setter Property="Background" TargetName="border" Value="{StaticResource Button.Pressed.Background}"/>
<Setter Property="BorderBrush" TargetName="border" Value="{StaticResource Button.Pressed.Border}"/>
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Background" TargetName="border" Value="{StaticResource Button.Disabled.Background}"/>
<Setter Property="BorderBrush" TargetName="border" Value="{StaticResource Button.Disabled.Border}"/>
<Setter Property="TextElement.Foreground" TargetName="contentPresenter" Value="{StaticResource Button.Disabled.Foreground}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

WPF - TextBox style remains default settings when Triggers fire

I have this Dynamic Resource to set my TextBox's styles:
<Style x:Key="TextBoxStyle" TargetType="TextBox">
<Setter Property="FontSize" Value="30"/>
<Setter Property="HorizontalContentAlignment" Value="Left"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="HorizontalAlignment" Value="Stretch"/>
<Setter Property="VerticalAlignment" Value="Stretch"/>
<Setter Property="BorderThickness" Value="2"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="FontFamily" Value="CenturyGothicRegual"/>
<Setter Property="Foreground" Value="#FF5B5B5B"/>
<Setter Property="Opacity" Value="1"/>
<Setter Property="BorderBrush" Value="#FF5B5B5B"/>
<!--<Setter Property="FocusVisualStyle">
<Setter.Value>
<Style x:Name="ActiveStyle" TargetType="{x:Type TextBox}">
<Setter Property="BorderBrush" Value="Black"/>
</Style>
</Setter.Value>
</Setter>-->
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="BorderBrush" Value="Black"/>
<Setter Property="BorderThickness" Value="10"/>
</Trigger>
<Trigger Property="IsFocused" Value="True">
<Setter Property="BorderBrush" Value="Pink" />
<Setter Property="BorderThickness" Value="15"/>
</Trigger>
</Style.Triggers>
</Style>
And the textbox that uses it:
<TextBox Grid.Row="2" Grid.Column="1" Margin="2,2,2,2" Style="{DynamicResource TextBoxStyle}"
FontSize="30" Text="asdasd" HorizontalContentAlignment="Left" VerticalContentAlignment="Center"
FocusVisualStyle="{StaticResource TextBoxStyle}">
</TextBox>
Again the problem is that when I hover over my mouse or click in the textbox, the border gets the default blueish colour. However the borderthickness does change when I set them (ugly that way but needed to debug). So how to get around this issue?

You need to override the ControlTemplate of the Button because there is a trigger in the default template that sets the BorderBrush property to a hardcoded value on mouse over:
<Style x:Key="TextBoxStyle" TargetType="TextBox">
<Setter Property="FontSize" Value="30"/>
<Setter Property="HorizontalContentAlignment" Value="Left"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="HorizontalAlignment" Value="Stretch"/>
<Setter Property="VerticalAlignment" Value="Stretch"/>
<Setter Property="BorderThickness" Value="2"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="FontFamily" Value="CenturyGothicRegual"/>
<Setter Property="Foreground" Value="#FF5B5B5B"/>
<Setter Property="Opacity" Value="1"/>
<Setter Property="BorderBrush" Value="#FF5B5B5B"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TextBox}">
<Border x:Name="border" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="True">
<ScrollViewer x:Name="PART_ContentHost" Focusable="false" HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden"/>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Opacity" TargetName="border" Value="0.56"/>
</Trigger>
<Trigger Property="IsKeyboardFocused" Value="true">
<Setter Property="BorderBrush" TargetName="border" Value="{StaticResource TextBox.Focus.Border}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="BorderBrush" Value="Black"/>
<Setter Property="BorderThickness" Value="10"/>
</Trigger>
<Trigger Property="IsFocused" Value="True">
<Setter Property="BorderBrush" Value="Pink" />
<Setter Property="BorderThickness" Value="15"/>
</Trigger>
</Style.Triggers>
</Style>

How to get rid of the default blue color on hover over a button?

I've declared a style as follows.
<Style x:Key="RightButtonStyle"
TargetType="Button">
<Style.Triggers>
<Trigger Property="IsMouseOver"
Value="True">
<Setter Property="Background"
Value="BlueViolet"></Setter>
</Trigger>
<Trigger Property="IsMouseOver"
Value="False">
<Setter Property="Background"
Value="Yellow" />
</Trigger>
</Style.Triggers>
</Style>
My button using the style does obey only the yellow part. For some reason it still gets bluish (default hover-over color) and not blue-violetish on hover. What am I missing? There are no other setters or styles that I'm aware of.

It's still using the default button template. You need to override it.
<Style Key="RightButtonStyle" TargetType="Button">
<Setter Property="OverridesDefaultStyle" Value="True"/>
<Setter Property="Margin" Value="5"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Button">
<Grid Background="{TemplateBinding Background}">
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center" />
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" Value="BlueViolet"></Setter>
</Trigger>
<Trigger Property="IsMouseOver" Value="False">
<Setter Property="Background" Value="Yellow" />
</Trigger>
</Style.Triggers>
</Style>

MenuItem Style override single role style

is there any way to override a single role style of MenuItem? I know the way to override the IsHighlighted color of MenuItem is to override the ContentTemplate. What i want is to override the ContentTemplate for Role "SubmenuItem"
<Style x:Key="ActionMenuItemStyle" TargetType="{x:Type MenuItem}">
<Setter Property="HorizontalContentAlignment" Value="{Binding Path=HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}" />
<Setter Property="VerticalContentAlignment" Value="{Binding Path=VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}" />
<Setter Property="Background" Value="Transparent" />
<Setter Property="Template" Value="{StaticResource SubmenuItemTemplateKey2}" />
<Setter Property="Foreground" Value="Black" />
<Style.Triggers>
<Trigger Property="Role" Value="TopLevelHeader">
<Setter Property="Padding" Value="7,2,8,3" />
<Setter Property="Template" Value="???" />
<Setter Property="Foreground" Value="White" />
</Trigger>
<Trigger Property="Role" Value="TopLevelItem">
<Setter Property="Padding" Value="7,2,8,3" />
<Setter Property="Template" Value="???" />
</Trigger>
<Trigger Property="Role" Value="SubmenuHeader">
<Setter Property="Padding" Value="2,3,2,3" />
<Setter Property="Template" Value="???" />
</Trigger>
<Trigger Property="Role" Value="SubmenuItem">
<Setter Property="Padding" Value="2,3,2,3" />
</Trigger>
</Style.Triggers>
</Style>
The {StaticResource SubmenuItemTemplateKey2} is my override ContentTemplate. For the other roles i want use the default templates of MenuItem. Is there any way to do it?
Best regards
Lutze

You're trying to override all the menu items and next trying to override it again (to set it back to default style). In this case you just need to override the menu item with role of SubmenuItem, so the code can be just like this:
<Style x:Key="ActionMenuItemStyle" TargetType="{x:Type MenuItem}">
<Setter Property="HorizontalContentAlignment"
Value="{Binding Path=HorizontalContentAlignment,
RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}" />
<Setter Property="VerticalContentAlignment"
Value="{Binding Path=VerticalContentAlignment,
RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}" />
<Setter Property="Background" Value="Transparent" />
<Setter Property="Foreground" Value="Black" />
<Style.Triggers>
<Trigger Property="Role" Value="TopLevelHeader">
<Setter Property="Padding" Value="7,2,8,3" />
<Setter Property="Foreground" Value="White" />
</Trigger>
<Trigger Property="Role" Value="TopLevelItem">
<Setter Property="Padding" Value="7,2,8,3" />
</Trigger>
<Trigger Property="Role" Value="SubmenuHeader">
<Setter Property="Padding" Value="2,3,2,3" />
</Trigger>
<Trigger Property="Role" Value="SubmenuItem">
<Setter Property="Padding" Value="2,3,2,3"/>
<!-- override here -->
<Setter Property="Template"
Value="{StaticResource SubmenuItemTemplateKey2}"/>
</Trigger>
</Style.Triggers>
</Style>
Otherwise (following your original approach), we may need some dummy MenuItem element which has the default style. Then we can Bind the Template of whatever items to the Template of that dummy element to restore their default style.