RibbonCombobox: orange border is appeared after changing color

I’ve got a simple ribbon combobox (MS Ribbon for WPF) and try to change its style. When I set properties "PressedBackground" and "PressedBorderBrush" to any colors, an orange border is appeared.

See screenshot:

enter image description here

XAML:

<ribbon:RibbonComboBox SelectionBoxWidth="110" PressedBackground="Blue" PressedBorderBrush="Black">
    <ribbon:RibbonGallery></ribbon:RibbonGallery>                                                    
</ribbon:RibbonComboBox>

Any ideas to remove this border?

Solution

In order to change that you must edit the RibbonComboBox template and change where that Orange border appears, to do that i prefer using Blend or the Vs designer :

Select the RibbonComboBox control,

Convert the RibbonComboBox to local resource in the properties window:

enter image description here

Under the IsChecked Trigger change the InnerBorder from the gradient Orange,

<Trigger Property="IsChecked" Value="True">
 <Setter Property="Background" TargetName="OuterBorder" Value="{Binding CheckedBackground, RelativeSource={RelativeSource TemplatedParent}}"/>
 <Setter Property="BorderBrush" TargetName="OuterBorder" Value="{Binding CheckedBorderBrush, RelativeSource={RelativeSource TemplatedParent}}"/>
 <Setter Property="BorderBrush" TargetName="InnerBorder">
  <Setter.Value>
    <LinearGradientBrush EndPoint="0,1" StartPoint="0,0">
     <GradientStop Color="#FFE7CBAD" Offset="0"/>
     <GradientStop Color="#FFF7D7B5" Offset="0.1"/>
     <GradientStop Color="#FFFFD38C" Offset="0.36"/>
     <GradientStop Color="#FFFFC75A" Offset="0.36"/>
     <GradientStop Color="#FFFFEFA5" Offset="1"/>
    </LinearGradientBrush>
  </Setter.Value>
 </Setter>
</Trigger>

To whatever color you want :

<Trigger Property="IsChecked" Value="True">
 <Setter Property="Background" TargetName="OuterBorder" Value="{Binding CheckedBackground, RelativeSource={RelativeSource TemplatedParent}}"/>
 <Setter Property="BorderBrush" TargetName="OuterBorder" Value="{Binding CheckedBorderBrush, RelativeSource={RelativeSource TemplatedParent}}"/>
 <Setter Property="BorderBrush" TargetName="InnerBorder">
 <Setter.Value>
  <SolidColorBrush Color="Red"></SolidColorBrush>
</Setter.Value>

Output :

enter image description here