This rubbish that Europeans developed white skin only 6000 years ago also needs to come to an end. Both Cheddar Man and LaBrana Man were likely South Asian in origin. LaBrana Man carried Haplogroup Y-DNA C6 and its likely Cheddar Man also carried this Haplogroup. Haplogroup C is South Asian in origin.
If Neanderthal genes are still influencing the skin colour and hair colour of modern Eurasians, its likely this goes back to the interbreeding with Neanderthals.
Oldest remains found with blonde hair is dated 15 000 years and the remains were found in Russia. Oldest European with blonde hair, blue eyes and white skin is dated 7700 years and was found in Sweden.
7700 Motala Man:
Light (not necessarily "European pale") skin certainly predates 6000 years ago by a really large margin, but it's nonsense to say "haplogroup C is South Asian in origin, so Cheddar Man and La Brana were South Asian". By that same token, R1b and R1a probably come from P, and P
also probably came from South Asia or Southeast Asia, so it seems R1b and R1a ancient males from Europe were no European either, but South/Southeast Asians. As I said, that statement does not make sense.
Haplogroup C is
very old (~53 kya), so by the time of La Brana there had been dozens of thousands of years for the dispersal of C males, and some clades of C are as old as or even older than the haplogroup R as a whole (R1*, R1a, R1b, R2)! Besides, Y-DNA haplogroups do not determine one's ancestry as a whole, actually it accounts for a tiny portion of one's ancestry and can easily become disconnected from the autosomal DNA. Cheddar Man and La Brana were WHG, and EHG were nothing but WHG + a bit of ANE and CHG-like. By that token then there are actually no Europeans at all, because all of them come from WHG ("South Asian" apparently if we're going to determine that based on the origin of the most basal form of Y-DNA haplogroups), EHG (also "South Asian", but with "West Asian" and "North Asian"), ANF ("West Asian") and later extra CHG and Iran_Neolithic ("West Asian" too). If people like La Brana and Cheddar Man, who lived in Europe since the Late Paleolithic at least, were not indigenous Europeans, then no one else is.
I'm not sure the Motala man had blonde hair, are you sure about that? The main fact I believe light skin (but I think it was initially more "Sicilian light skin" than "Scandinavian light skin") dates to before 10,000 years ago is that the main genes for light skin were present (not necessarily together yet) in ANF, CHG, Iran_Neolithic (only SLC24A5, though), Levant_Neolithic, EHG and SHG. Those populations had diverged from each other much earlier and lived too far from each other, but by the Early Neolithic they all had some of the main mutations for light skin. That suggests to me that there had been enough time for the derived alleles to spread significantly, even if they were not fixed yet.
As for Neanderthal genes influencing in skin and hair color, scientists have already asserted that the gene alleles contributed by Neanderthals are
NOT the main determinants of light skin and light hair in modern West Eurasians (or East Eurasians for that matter). The case seems one of convergent evolution, because the alleles humans inherited from neanderthals have a minor contribution, they're not decisive like the skin-lightening mutations in SLC24A5 and SLC45A2 in modern West Eurasians. Remember that skin color is defined by at least 70 (IIRC) different gene variants, it's a cumulative trait, but a few of them have a much higher impact than others. In my opinion, it's probable that Northwest Eurasian people who lacked the main derived alleles that are decisive to "modern" light skin already looked lighter than, say, their tropical African or South Asian cousins, but those mutations they carried were not "powerful" enough to make them look anything close to a white skin. They were probably moderately brown.