Over the past couple of years, I've found that I've had really good luck trolling with crank baits that have a UV finish. Recently, I had a great day on upper LOZ using a #5 Shad Rap in the green UV finish--plenty of crappies, channel cats and one lone white (also largemouth and a big drum).

Has anybody else found that UV (ultraviolet) finishes are triggers for crappies?