Adding Your Own Colors
When you are working with the Colors portion of ID, you can click on the small button labeled "+ color" at the top of the scrolling list of color chips. A small dialog appears and you can then move your cursor anywhere on your screen and press the space bar. ID picks up the color over which the cursor is positioned and you can then simply click on "OK" in the dialog. Then click on the "Save" button in the bottom right corner of ID and you've created a new color you can use in all your stacks and applications.
Adding Custom Controls
You can add a new control to your ID arsenal as well. Just create the control in Revolution (using ID for the things it's good at), select the control, go to the Controls section of ID and click "+ Control".
Think of the possibilities of creating whole libraries of controls and groups that carry with them the behavior and appearance you want repeated throughout your application.