XML : Can I change the color?

I am using the following code to make a star button:

  <Button      android:id="@+id/leftButton"        android:onClick = "Star"      android:layout_width="100dp"      android:layout_height="100dp"      android:Color="#FFFF00"   //I tried adding this, but no luck :(      android:layout_alignParentTop="true"      android:background="@android:drawable/btn_star" />    

The button currently looks white:

Is there anyway I can make it yellow?

I know I can't have two background attributes, but is there anything I can do to change the color of this star? I want to keep the star as a background attribute, rather than a source attribute, because I want to be able to change the size of it.