The part that you’re referring to is a little closer to the color as stands by itself. I also had wipe to infill turned on and I’m not entirely convinced that the “opaque red” is really 100% opaque.

I had to search for a while to find a good red that I liked. I really want to try Dragon Red by Materio3D (link) but they’ve been out of stock for a while, even on Voxel Factory’s website so I think they’ve stopped making it.

I printed on a MK3S+ with MMU2s. The modifications I mentioned in my other comment have made it rock solid, a couple thousand color changes on this print without issue.