Dynamically change the Border Background by setting property in xaml - wpf

Question

I'm trying to dynamically change a Border Background property named "Brush2", but I get the following error.
Unable to cast object of type 'System.Windows.Media.Color' to type
'System.Windows.Media.Brush'.
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Color x:Key="Brush0">#7F605F5F</Color>
<Color x:Key="Brush1">#7F7E7E7E</Color>
<Color x:Key="Color2">#7FFDFDFD</Color>
<SolidColorBrush x:Key="Brush2" Color="{DynamicResource Color2}" />
<Color x:Key="Brush3">#7FFFFFFF</Color>
<Color x:Key="Brush4">#BFFFFFFF</Color>
<Color x:Key="Brush5">#F2FFFFFF</Color>
<Color x:Key="Brush6">#FF6096E5</Color>
<Color x:Key="Brush7">#FF9B7C35</Color>
<Color x:Key="Brush8">#FFB0BAA1</Color>
<Color x:Key="Brush9">#7F60605F</Color>
<Color x:Key="Brush10">White</Color>
<Style TargetType="{x:Type TabItem}" >
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabItem}">
<Grid>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<!-- silver -->
<VisualState x:Name="Selected">
<Storyboard>
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Panel.Background).(GradientBrush.GradientStops)[0].(GradientStop.Color)" Storyboard.TargetName="border">
<EasingColorKeyFrame KeyTime="0" Value="{DynamicResource Brush8}"/>
</ColorAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Panel.Background).(GradientBrush.GradientStops)[1].(GradientStop.Color)" Storyboard.TargetName="border">
<EasingColorKeyFrame KeyTime="0" Value="{DynamicResource Brush8}"/>
</ColorAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Border.BorderBrush).(GradientBrush.GradientStops)[1].(GradientStop.Color)" Storyboard.TargetName="border">
<EasingColorKeyFrame KeyTime="0" Value="{DynamicResource Brush0}"/>
</ColorAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Border.BorderBrush).(GradientBrush.GradientStops)[0].(GradientStop.Color)" Storyboard.TargetName="border">
<EasingColorKeyFrame KeyTime="0" Value="{DynamicResource Brush9}"/>
</ColorAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Normal"/>
<VisualState x:Name="MouseOver">
<!-- bronze -->
<Storyboard>
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Panel.Background).(GradientBrush.GradientStops)[0].(GradientStop.Color)" Storyboard.TargetName="border">
<EasingColorKeyFrame KeyTime="0" Value="{DynamicResource Brush7}"/>
</ColorAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Panel.Background).(GradientBrush.GradientStops)[1].(GradientStop.Color)" Storyboard.TargetName="border">
<EasingColorKeyFrame KeyTime="0" Value="{DynamicResource Brush7}"/>
</ColorAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Border.BorderBrush).(GradientBrush.GradientStops)[1].(GradientStop.Color)" Storyboard.TargetName="border">
<EasingColorKeyFrame KeyTime="0" Value="{DynamicResource Brush0}"/>
</ColorAnimationUsingKeyFrames>
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Border.BorderBrush).(GradientBrush.GradientStops)[0].(GradientStop.Color)" Storyboard.TargetName="border">
<EasingColorKeyFrame KeyTime="0" Value="{DynamicResource Brush9}"/>
</ColorAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Flashing">
<Storyboard>
<DoubleAnimation
Storyboard.TargetName="BorderGlass"
Storyboard.TargetProperty="Opacity"
From="0.0"
To="1.0"
Duration="0:0:0.33"
AutoReverse="True"
RepeatBehavior="Forever"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Disabled"/>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Border x:Name="border" BorderThickness="3" CornerRadius="5,5,0,0">
<Border.BorderBrush>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="{DynamicResource Brush0}" Offset="0"/>
<GradientStop Color="{DynamicResource Brush1}" Offset="1"/>
</LinearGradientBrush>
</Border.BorderBrush>
<Border.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="{DynamicResource Brush6}" Offset="0.004"/>
<GradientStop Color="{DynamicResource Brush6}" Offset="0.823"/>
<GradientStop Color="{DynamicResource Brush10}" Offset="0.228"/>
</LinearGradientBrush>
</Border.Background>
</Border>
<Border x:Name="BorderGlass" BorderThickness="3" CornerRadius="5,5,0,0" Background="{DynamicResource Brush2}">
<Border.BorderBrush>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="{DynamicResource Brush3}" Offset="0"/>
<GradientStop Color="{DynamicResource Brush4}" Offset="0.401"/>
<GradientStop Color="{DynamicResource Brush5}" Offset="0.254"/>
</LinearGradientBrush>
</Border.BorderBrush>
</Border>
<ContentPresenter HorizontalAlignment="Center" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="Center" ContentSource="Header"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ResourceDictionary>

Answer 1

What you need to do is set the brush to something like a solidcolorbrush object. http://msdn.microsoft.com/en-us/library/system.windows.media.solidcolorbrush.aspx
The constructor takes a color object.

Answer 2

The following code works, but I had to do this:
Uri uri2 = new Uri("/Resources/DayModeTab2.xaml", UriKind.Relative);
ResourceDictionary resDict2 = Application.LoadComponent(uri2) as ResourceDictionary;
//Make some changes
MobileApp.Get().Resources.MergedDictionaries.Add(resDict2);
And also my poor naming scheme caused conflicts since I have Brush0 in 2 xaml files.
<Border x:Name="BorderGlass" BorderThickness="3" CornerRadius="5,5,0,0" >
<Border.Background>
<SolidColorBrush Color="{DynamicResource Color2}" />
</Border.Background>
<Border.BorderBrush>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="{DynamicResource Brush3}" Offset="0"/>
<GradientStop Color="{DynamicResource Brush4}" Offset="0.401"/>
<GradientStop Color="{DynamicResource Brush5}" Offset="0.254"/>
</LinearGradientBrush>
</Border.BorderBrush>
</Border>