I signed up for a week-long summer course in Colour Theory in the NCAD in the summer of 2004, but I found it too boring and didn't attend after the first day. Maybe I should have stuck to it, or maybe I should have got myself a good book about colours instead. I have such a book now, Blue and Yellow Don't Make Green, and I'm actually enjoying it. It tells you how to mix bright colours, not mud! It follows the same principles as what I picked up on that one day in the NCAD, i.e. you need 2 yellows, 2 blues and 2 reds in order to create bright colours, but the reasons why are very well explained (if a bit repetitively).
So, I spent a bit of time mixing colours this afternoon, greyed violets and bright violets. I should have allowed myself more room at the blue end. Maybe I should do another series with the same basic colours, and start the mixing with the blue instead of the red!