How can I change the star colors and size of the stars?
Step #1: Create your own style, by cloning one of the existing styles (from $ANDROID_HOME/platforms/$SDK/data/res/values/styles.xml), putting it in your own project's styles.xml, and referencing it when you add the widget to a layout.
Step #2: Create your own LayerDrawable XML resources for the RatingBar, pointing to appropriate images to use for the bar. The original styles will point you to the existing resources that you can compare with. Then, adjust your style to use your own LayerDrawable resources, rather than built-in ones.