It’s hard to say where it’s the most apparent, by it feels fleshy tones are the most obvious, try eac79d / 234 199 157
I’m getting the effect with almost every brush to varying degree, but it’s easily replicable with the default classic smudge in the smudging group, as seen in the image. The only thing I’ve done is set the layer to pigment and used the smudge on the same layer.
The only setting I’ve found to affect this is wetness at 100% minimising the effect drastically, probably because it doesn’t sample the darkened areas so it doesn’t snowball from there.
Edit: Not sure if this helps, but when used with pure white, the effect is clearly pushing towards red
Edit2: This is an issue with the smudge engine that I’ve noticed long before this update, but is really exacerbated in combination with the pigment mode. The last image shows the same default classic smudge brush used on a pure white layer and producing a similar artefact without using the pigment mode, but much more subdued, lacking the reed tint, and requiring overworking the area more, so the issue likely doesn’t actually lie in the pigment mode itself.