a little something like this ..... (By the way, this xaml is WPF, not silver light, which is a little different)
<style TargetType="{x:Type Button}">
<Setter Property="Background" Value="Green">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Button">
<Grid Background={TemplateBinding Background}
</ControlTemplate>
</Setter.Value>
</Setter>
</style>
Now, as soon as you apply this style to the object, whenever you set the background of this object, the template will use the Background property (this property in the button control), and by default what you set to the style (in this case green)
, , DependencyProperty INotifyPropertyChanged . - .