Took a quick peak at my top 10 list and I can't say there's much of a trend, there's more black than any other colour but that's just a product of like 40% of all anime characters having black hair lol, I can say I very highly appreciate when a character has pink hair tho but I don't gravitate towards them just for that. I think I also tend to highly enjoy the black haired mc with blonde haired bff/rival/whatever but again it's such a common trope that I don't even need to gravitate towards it it's just so many anime duos have it going on lol