Problem:

Changing theme colors using the admin area failed.

Solution:

The logo.png file was missing from the theme's root folder, probably causing a uncaught exception that caused the bug. After locating the image file in thr correct place (root folder), the problem ceased.

Pre-defined color schemes

Pre-defined color schemes are declared in 'color.inc' file, as an array inside 'schemes' array, and are executed in 'preview.js'. So we can use these 2 files to add color definitions to the theme.