I figured it was a 50-50 tossup on any relationship there. And that'd be a rather interesting Loroi...hmm, gives me some new ideas for Sunfire at any rate.
I've done the color overlay thing a few times myself and it can be annoying sometimes. Sometimes it helps, other times, I have to go at that layer with an eraser to rescue some colors underneath. It's not to say someone couldn't use some sort of magical color overlay from their clothes to make themselves blend into them and the environment though.
Hmm, pale-skinned humans usually can
pull off the ethereal pretty well, so I can see what you mean by not going into the crazy skin colorations unless the person's of another race. I usually figure, for "unnatural," pale or unusually colored skin, unusual hair/eyes tend to work.
In your case of Second Six, one way you could do it, is to have the Magic be something that makes a person look a bit unnatural and/or ghostly. Perhaps the stronger the magical heritage, the stronger the odd-lookingness. The more human a person is, the more natural they look? This can get mixed up with how some people naturally look a bit off, or ghostly themselves (ie. albinos, pale skinned people, unusually light hair, all of which can be found in nature). I'd imagine that kind of society would place a lot of stock on appearance if Marks are usually fairly obvious...
I think I'll cut the rambling now.