Back in the good old days when they were piddling around trying to fit bones together it was hard to get a good fit so you could figure out hair color. Now we know the Neanderthals had red hair, and if you think that's a problem ..... well, it's not a problem. There are 200 million people in this world with red hair and even more with mixed colored hair and they don't think it's funny at all. So, if you want to laugh and joke about it watch your back. They are lurking around night and day ready to fly into a rage, flash those blue/green eyes and use whatever is handy as a cudgel.
It was good for the Neanderthals to be redheads. Life was tough back in the day.
(NOTE DNA researchers say it was a different gene than the modern gene for red hair, but the principle is the same ~ and there's a reason the saber toothed tigers are gone).
Is the fact that the red hair gene is different a new finding?
The first time I ever saw the proposition that Neanderthals and homo sapiens had interbred, part of the evidence presented was that both Neanderthals and modern humans have members with red hair. I'll admit that I was not convinced by the argument; it's completely possible for color pigments in different species to arise independently. (With the new genetic evidence, I'm still on the fence about the whole thing; if Neanderthals and homo sapiens were interbreeding, then they weren't different species.)
Unfortunately, with DNA evidence on people long dead, you have much the same problem as the old bone-splicers of old - which is that modern investigators are piecing together disparate pieces of evidence to make them fit the picture that has already been pre-determined. In other words, the evidence tends to be made to fit the theory, instead of the other way around.