Is there a way to colour code tabs?
mm.
No. But you might be able to repurpose the linksets for the task. In the screenshot, I have marriage books marked with the green "C" linkset:
Ok thanks, but not exactly what I'm looking for. I imagine it's been suggested already.
I don't know that it has been suggested...I think it's a good idea. You might want to post in the suggestion forum and see what happens. If you post it as a suggestion, you might want to also add some reasons why it might be helpful.