I've dove into Android development recently at work, and have found that theming all the various components seems more complicated than I'm used to in good ol' CSS.

Luckily, I've discovered that there are tools out there for Android similar to Bootswatch which let developers generate styles for many of the basic native UI components. A developer can generate all the assets necessary to use custom colors in their app in a way that's internally consistent, as well consistent with Android Material or Holo design standards.

Some cool tools I found include:

Android Holo Colors - Create many of the basic UI widgets in a color of your choosing

Android Asset Studio - Generate icons in all the sizes you need for the launcher, action bar, notifications, etc. on various devices.

Action Bar Generator - Though deprecated, you (like me!) may still be using the action bar.