Red head symbolism

In my other post I mentioned that I thoroughly enjoyed this movie, but I forgot to address something that's gnawing at me. Right from the get-go, this movie is saturated with redheads. All the female supporting roles are redheads, as well as a large amount of this kids in the class. Does anyone have any clue as to why this choice was made? The only analysis of symbolism I can make is a poor attempt in which I use Southpark's 'gingers have no souls' quip to suggest all the gingers in Collins' life have sucked up his souls, too.

Amusing though that theory may be, I doubt that this is the story the director meant to tell with his use of so many redheads. Would love to hear other people's thoughts.