Where is the DependencyProperty defined? On the same Window/UserControl? If you simply want to bind to the value of a DependencyProperty you probably want to use regular {Binding ...} syntax instead.
Example 1: If you are binding to a dependency property on a particular control named myControl you can declare it like below.
Background="{Binding ElementName=myControl, Path=Color1}"
Example 2: If you don't want to rely on naming controls because it is so pasay in WPF and you are referencing a property defined on your Window you could do something like below.
Background="{Binding RelativeSource={RelativeSource AncestorType={x:Type Window}}, Path=Color1}"