Whitedice, carp will eat many things from nymphs to crayfish to small baitfish & vegetation. I once read that orange was a good color, and have had some good success with flies that incorporate orange. But, I've caught them on other colors as well. Olive, black, & brown shades all seem to do well at times. In muddy water I think dark colors might do best, but you have to get it in front of them without spooking them. That's the main thing.
Best to keep the flies simple IMO, a basic profile that might imitate a variety of things, and of a size that fits both the waters & the size of the fish, and your equipment. I use flies tied on size 2, 4 or 6 the most and an 8 wt. I've caught smaller ones on a 6 wt too.
Here's some flies I've had some success with. There are others in wide use & a search for carp flies will give you more. These are simple, a dubbed body, a tail of rabbit fur, (or other soft textured hair) and a wing or collar of similar hair. Sometimes a couple of strands of flash, like copper, gold or bronze helps.