<Window x:Class="WpfApplication1.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="" Height="300" Width="300"> <Canvas> <TextBlock Text="Brush from ARGB Color [ .Fill = new SolidColorBrush(Color.FromArgb(100, 0, 0, 255)); ]"/> <Rectangle HorizontalAlignment="Left" Width="60" Height="20"> <Rectangle.Fill> <SolidColorBrush> <SolidColorBrush.Color> <Color A="100" R="0" G="0" B="255" /> </SolidColorBrush.Color> </SolidColorBrush> </Rectangle.Fill> </Rectangle> </Canvas> </Window>