I've edited this thread

What I originally thought was an issue between textures in CAS and in live mode turns out to be a little more complicated than that. Yes, all my textures look perfectly fine in CAS and then turn weird in game. Digging deeper though it seems like the issue only pertain to certain colors or ranges of colors.

Each top uses the same multiplier, as does each mankini (well, kind of. There is a second multiplier with a zipper texture added but it's otherwise the same, especially in the circled areas). The masks are identical per package. The first channel is pure red (255,0,0), second is yellow (255,255,0) and, in the case of the bikini top, the third is magenta (255,0,255). Each channel was created on its own layer and then merged together to prevent odd bleeding between the colors.

Additionally, changing the skintone of the sim but leaving the channel colors the same does affect the bleeding as well. In that picture, it's the same sim, same bikini, same channels, literally just a different, darker skintone.

Is this something I can fix or is it some weird game thing I've just never noticed before and will have to live with? I'm totally baffled right now.