two more relevant ideas
1. maybe it would be the best, if i could define my project colors in Project info panel.
2. at least, you should automaticaly add the Links and Selection colors to the colors panel, plus 8 others userdefined, so the color panel would have 1 more row of 10 project colors, with internal names e.g. user0 to user9, so that they could be easily incorporated in the symbols without other extra hacks, and so that changing e.g. user0 color to something else would repaint all the mockups in the project, the same way as it is now with changing Links or Selection colors