Red colored horses do have more sensitive skin: Mister and Scotch for instance. It can lead to irritability but really they are just sensitive.
I strongly prefer mares. With a gelding you're always guaranteed at least 80%. They are consistent. Mares will always give you 100%... 100% fail or 100% success.
I personally would rather have a couple days in a dirt if I can have a day in the sun.
Mares do have more ups and downs but feminism has proved that hormones aren't a legit reason to exclude women from the workplace.
Blue eyes are more light sensitive so in bright weather or snow it can be a problem. But the real superstition was blindness. Science has made us smarter to differentiate a blue pupil from a blue iris.
The hated of white is connected to the believe that white legs make white feet and white feet are weak. It's one of many reasons that led most white marked horses to not being able To be registered. Even AQHA is registering horses with too much white now.