Thanks @Ashley for the feedback, The thing is, I have many tabs opened and remembering colors for them would require extra effort, I don't think anybody looks for tabs by the color. Then I happen to close one (accidentally or because I don't need it for a long time), and it changes color - but as I said, I'm not bothered about it changing color because I don't look at colors anyway. I just think so many colors don't look good
Regarding Potato's suggestion, #1 yes would be nice, #2 and #3 I'm not sure, I think I prefer to have the same color for all projects, as long as event sheets and layouts have different color tabs (or some icon).
Another small suggestion while I'm at it, I think it would be nice to have "numbers" or something assigned to open windows / tabs, and to be able to switch to them using hotkeys, e.g. Alt+1 would switch to first tab, Alt+2 to the second etc. And the fact that we can reorder them, as we can today, would make this useful even if we accidentally close tabs.