Galicia is paradoxical because it is reputed to be the most genuinely celtic region in Spain, and yet the percentage of haplogroup R1b is relatively low. It also has a reputation as the region of Spain with the highest percentage of light hair and blue eyes. Well, I can say that after traveling for the rest of Spain this is true, but the difference is very subtle.
In my opinion blondism is closely linked with haplogroup I than with haplogroup R1b, and in Galicia there is the highest prevalence of haplogroup I (M253). That might explain that light hair is slightly higher than in the rest of Spain, although I notice that most of the Galician are brown haired or brunette.