I read in Bill Dance's 101 Tips for Freshwater Fishing that a light draws insects which draw in baitfish to feed on the insects and the crappie feed on the baitfish. Also, I use an Arbogast Jitterbug at night for giant crappie. The popping sound and rattle really draw 'em in.
Crankbaits 4 LIFE!!!!!!
A white light in the boat will certainly attract insects. Personally, I don't want to attract insects.
The light I use is a submersible green light. It attracts plankton, which attracts shad, which attract stripers and crappie.