SolidColorBrush's color is specified using 6-digit hexadecimal notation.
<Window x:Class="WpfApplication1.ShapesWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="ShapesWindow" Height="160" Width="400"> <Window.Resources> <Style TargetType="{x:Type Rectangle}"> <!-- Gives all the rectangles in this panel a white stroke. --> <Setter Property="Stroke" Value="White"/> <Setter Property="StrokeThickness" Value="1"/> </Style> </Window.Resources> <Canvas> <Rectangle Width="50" Height="50"> <Rectangle.Fill> <SolidColorBrush Color="#0000FF" /> </Rectangle.Fill> </Rectangle> </Canvas> </Window>