I think more than color, it seems to run in families.
Anybody that has come from Goldie X Skippy = Curious as a cat, very friendly to humans,
Dolly X Skippy = Curious and super human friendly,
Boo X Skippy = HUGE, loving and friendly to humans but more vigilant.
Goldie & Mort are the horses I say were Siamese cats in another life, scared of NOTHING and want to stick their noses into everything. Mort especially liked to grab stuff most horses were terrified of (tarps, feed sacks) and flap them around and chase his pasture mates. Goldie (buckskin), Mort (cremello), Skippy (cremello).
Dolly (bay), Boudreaux (palomino), both are very lovey and curious. They love to meet you in the pasture for scratches and will follow you around just to see what's up.
Boo (Chestnut), Beaux (chestnut), Twoey (chestnut), Ducati (palomino), and Kokopelli (Joker) (palomino), very sweet natured but more vigilant.
I've got Boo, Goldie & Dolly all 3 back in foal to Skippy this year, be fun to see if it all holds true.
Oh and I did do Patti (HZ black Tobi) X Skippy and got Chippy (smokey Black tobi) who was very friendly and human oriented right from the minute she hit the ground. Lots of fun to work with as a baby. She left here when she was weaned, and went to the west coast, so haven't seen what she was like to get under saddle. I suspect pretty darn easy. Patti was and so was her previous foal, Harley by RA Hot Every Night. Super easy to handle, but Patti is my SUPER fave mare, so haven't used her as a broodie much.