Being Swedish I grew up with the Norse mythology and I thoght it was really interesting and fun. And in the norse mythology Tor was always described as having red hair. And even though Marvel-Thor looks great as a blonde, it thought it would be fun to make him a red-head.
I'm not really a marvel-fan, but I think it's fun that the norse mythology has a small part in it (even if it's pretty far from the "original" mythology)
Also, I haven't drawn a man in ages, so that was fun
(This version of Thor belongs to Marvel, I guess)