For that kind of bar you can use a repeating linear gradient, something like this:
<Grid
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Border Background="Black" Padding="2" Width="500" Height="20">
<Grid Width="{Binding Value, ElementName=progress}" HorizontalAlignment="Left">
<Rectangle>
<Rectangle.Fill>
<LinearGradientBrush StartPoint="0,0" EndPoint="175,0" MappingMode="Absolute" SpreadMethod="Repeat">
<GradientStop Offset="0" Color="#ffcca742"/>
<GradientStop Offset="0.99" Color="#ffcca742"/>
<GradientStop Offset="0.99" Color="#00cca742"/>
<GradientStop Offset="1" Color="#00cca742"/>
</LinearGradientBrush>
</Rectangle.Fill>
</Rectangle>
<Rectangle Height="2" VerticalAlignment="Bottom" Fill="#b0ffffff"/>
</Grid>
</Border>
<Slider x:Name="progress" Minimum="0" Maximum="496" Value="400" Width="200" VerticalAlignment="Bottom" Margin="20"/>
</Grid>
Is that what you are looking for?