Ideas
Hi devinci35, how do you do this because when I made the default replacement for the default underwear with the nude bottoms diffuse, it shows the nude bottom in cas but when in live mode the black default boxers show under the pixels instead of the override nude bottoms like when a sim streaks or showers.
The other thing I would look at is turning off the mosaic during testing so that you can clearly see what is going on. Beyond that, make certain you have the right underwear. It's one specific top and bottom for the female sims and one specific bottom for the male sims. I would start with the female sims because that salmon color really stands out and is unmistakable. Do it for one clothing item, and see if it disappears. Then if that works, move onto the next. But like with any experiment, it's important to limit your variables.
Female Bottom: yfBottom_UnderwearSexy_Salmon
Female Top: yfTop_UnderwearSexy_Salmon
Male Bottom: ymBottom_UnderwearSexy_Black