Well if you want to get scientific. I learned this in my chemistry class. The human eye picks up three colors that normal catch attention: green blue and red. These colors, by catching attention send messages to the brain to imply interest. The male eye has more of a natural attraction to the color red. Hence, why most guys favorite color is red. So for most, like myself, red heads are a natural turn on (in most cases). But I also depends on if you're attractive too lol :-)
all I have to say is good question! hahaha my natural hair color is strawberry blonde, but it was more red than blonde (and obviosly I dyed it blonde, but I'm letting it go back to its natural color) And I have always had a nice complection for a red head not the typical fire crotch red hair with the pale neon white skin lol. And then also I've never actually heard a guy state whether he likes it or not...as a turn on at least. But seeing the answers guys say on here I'm surprised lol a lot more like the red heads.