He used models who were available to him, and most of them were more Meditteranean/Italian in appearance rather than anglo or germanic. Plus, if you think about it, the Holy Lands tended to have a lot of Greek/Roman features, rather than nubian or from deeper Africa or India. So, the Greek/Roman look was probably as accurate as was necessary.
As for the blond/blue-eyed look... that was always the ideal for the whole meditteranian area for what gods looked like. Wasn't Alexander the Great supposedly blond/blue-eyed? And there are still a very large number of people in the levantine area who are blond/blue-eyed, even though semitic.
So, thin k what you want, but blue eyes and blondish hair were probably the correct way of portraying Christ ( but not the nordic blond/blue eye look; more of a honey blond and a bit darker blue, a pig's eye blue).