Recently, I've found purple to be a hugely important hue in my flybox. When no other attractor nymph works, the purple Prince will. Then there's the blue midge, or the blue glo-bug. Blue? You can turn over a million rocks in the river, and never see anything remotely similar to a purple Prince (or regular Prince for that matter) or a blue midge. Yet they work. My theory is that differentiation is the real factor in play here ... and a good drift trumps all. Anyone with some good sources on colors as they relate to trout attraction, please chime in.