The one variable that we sometimes forget is the fact you don't know 100% if the fish are actually there or not. You might be fishing a chartreuse grub and get nothing, but by the time you switch to another color and drop it you suddenly start pulling up doormats maybe you just happen to be landing on fish that weren't there when you had chartreuse. Hell you can have two lines down with two different colors at the same time and one keeps getting bites and the other doesn't. Might just be the luck of the fact that the one getting bites happens to be traveling over fish while the other one is just a couple feet away. Until we can drop a camera down to watch the baits and see a fish pass up chartreuse for purple or any other color or vice versa, you really can't say for sure. Fluke are pretty voracious eaters. They are like the bluefish of the bottom. If they think something is or even might be food and they're hungry, they're gonna bite it.