Well, Moorish raids (in addition to those by the Vikings and various steppe peoples, particularly the Hungarian-Magyars) are often cited as one trigger for the developement of the European pattern of castle feudalism - a need for locally stationed, rapidly responding heavy cavalry to deal with the raiders and a network of local fortifications for them to operate from and to sustain ultimate territorial control in an emergency.

Incidentally, I wouldn't put all that much stock on the amount of contemporary commentary on the fair hair of the Celts and others. Contemporary witnesses did not, after all, recount so much what they saw but rather what made an impression on them; and for the Mediterranean peoples, used to fairly dark hair, blond hair would obviously have been an unusual and striking thing and thus draw disproportionate amounts of attention and commentary. Of course after the Romans conquered Gaul and the most of the rest of Celtic Europe (and settled to a long and very uneasy border with the Germans) the novelty sort of wore off and light hair among Germans would not by itself anymore merit much attention; red hair, if conspicuously more common than among the Gauls for example, conversely of course would.

It's sort of how the small numbers of armoured lancers in Sarmatian armies drew completely disproportionate levels of attention from their enemies, with the majority backbone of light horse-archers duly playing a second fiddle in contemporay accounts.