I'm 100% on board with suspended disbelief reason ( X happens because it is explainable by Y phenomenon which doesn't exist in our world yet does in a made up land such as Magicka ), but I find it hard to explain the following.
I have a character, for all intents and purposes, he was intended to be designed based on an Ashlander.(Ignore the outfit, he's low level in the following and wearing random stuff.)

Looks sweet enough eh? I decided to make him a vamp, I'm sure many know where this is going, but now in stage 3 (was about the same in stage 1 and 2) he looks like this:

Why would his tattoo all but disappear because his skin whitened? Maybe this is just a thing with vamps?

Nope, my Khajiit's tattoo stood out even more as one would expect. His stripes faded and became less visible, but those are a coloration organic to his body which would be expected to change with the rest. Maybe ZOS made the tattoos a part of the skin like a khajiit's stripes. Since it functions properly on the Khajiit, there's really no reason why this should be different on another race. One would think in developing, a tattoo on one char should be in the same layer as the other.
And so did many brave men, women, and beast fall to the end of Beta, never to be heard from again. All that is left, is whispers of the adventures they had.