to the cold northern climate
Yet the light coloration has nothing to do with cold adaptation, but only the UV-light skin exposure.

Also it might be related to the specific diet of people which had got not enough Vitamin D through their food.

Thats, together with the possibility of social-sexual selection, a possibility which leaves open when the process of depigmentation of Aurignacoids began and how long it lasted.

Just remind you that every evolutionary trend can be stopped at any time, if the selective conditions change. So probably it lasted from - to and stopped somewhere because the selective regime changed or the like, we can't say for sure, but it seems to be very likely to me that the process went on through Neolithic times AT LEAST.

Its quite sure that new colonists made it up to the North in Neolithic times, so later Mediterranoids, now those might have mixed up and became selected for the same traits older waves might have already acquired, so that the darker colorations didn't made it into modern times as good.

Really a lot of possibilities. We can be sure once we are able to test the bones and remnants with certainty for pigmentation and other genetic traits, than we can say how much continuity, population movements, which traits appeared when etc. in a more secure way.

It's really up to the (hopefully) upcoming research.