Thank you! I liked the way it turned out as well, couldn't stop playing with it myself.
The color mixing was easier then I had expected, because the entire fluid consists of multiple balls/drops, the lot of them together mix the colors smoothly enough, while the actual mixing between 2 drops/colors is a single step (sum of both their color values divided by 2).
BTW, Flash uses a fixed framerate (25 fps in this case), so fps is only usefull in relation to the nr of drops. I'm mostly interested at around what nr of drops, fps start to fall for you. I keep fps steady up to around 50-60 drops at normal size.