This file defines/lists the named colours as seen in a default Tinderbox file. Colour values may be defined, it appears, by any of the supported colour declaration methods: (HTML) name, RGB, hex, HSV. Most of the defaults use hex format declarations. The 'screen' name given to the file is for UI use so, 'red' could be defined as a green!
The (inclusion of and) order of colours seen in UI listings is in bit-wise alphabetical order - i.e. all initial uppercase words come first (i.e. 'Yellow' sorts before 'blue'). One exception to this is the programs' Colors menu, where the inclusion/order is set via the menus.xml file.
The application should be re-started after editing these files to ensure changes are detected. At minimum, the document(s) needing to show the change should be re-opened, should an app re-start be inconvenient at that time.