I have a horse with 2 blue eyes and lets just say she's not the greatest horse to be around all the time, the best way to explain her is bipolar or almost like split personality (obviously I know that's not the case, just a way to explain it). I personally think she is like this from when she was a baby nd she was abused and after the people took her back from the person they sold her to she was just used for staff to take people out on trails and barrel racing, obviously they didn't do much on ground manners with her and teaching her to respect people, it was just basically her and the herd. She also is VERY hormonal.
When ever the owner of the barn is around and she see her acting up, she always says "you know she's probably like this because of her blue eyes, the horses blue eyes aren't how you and I would get them, they are missing something in their brain (i don't remember what she said it was) that most other horses have and that's why she can be crazy and flighty."
But see i've talked to many people with blue eyed horses and their horses are completely sane, where I have seen horses with brown eyes who are crazy.
What do you think, is she missing something in her brain and that's why she has blue eyes?