LinearGradientBrush
может удовлетворить ваши потребности.
<Page.Resources>
<LinearGradientBrush x:Key="TestGradient" StartPoint="0,0" EndPoint="1,1">
<LinearGradientBrush.GradientStops>
<GradientStop Color="Red" Offset="0.0"/>
<GradientStop Color="Red" Offset="0.3"/>
<GradientStop Color="White" Offset="0.3"/>
<GradientStop Color="White" Offset="0.8"/>
<GradientStop Color="Red" Offset="0.8"/>
<GradientStop Color="Red" Offset="1"/>
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
</Page.Resources>
<Grid>
<TextBlock Text="535" FontSize="50" HorizontalAlignment="Center" FontWeight="Black" Foreground="{StaticResource TestGradient}"/>
</Grid>
![5ee687ca-82a4-4013-8e21-9b523f01cec3.png](https://storage.live.com/items/51816931BAB0F7A8!13827?authkey=AO7QXpgYo7-5DUU)