I use all kids of crazy colors together. Never prewash. White background with bright colors. Back and white. I haven't had any problems except a couple of weeks ago. I washed a red, white and blue wall hanging. I know I have washed it before without problems. For some reason one of the reds ran into one of the whites, there are 6 different whites. It came out when I washed it in OxyClean.I just throw in a couple of color catchers.