I agree with what jill said about some not seeing well. We have a mare that has blue eyes with pink around her eyelids, and sometimes in the sunlight she gets blinded very easily. One time she ran into a handle of a wagon when it was right in front of her. So, I believe this can lead to them getting spooked, but I don't believe all blue eyed horses are that way, just the ones with pink skin for some odd reason.
Chasta