Use System Color to draw Line

   
       
<Canvas xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Line X1="48" Y1="48" X2="1000" Y2="48"
          Stroke="{DynamicResource {x:Static SystemColors.WindowTextBrushKey}}"
          StrokeThickness="12"
          StrokeDashArray="1 2 2 1" />
</Canvas>