the horses eye

Question
I read somewhere that if there is more white around the eye than there is color,
the horse has a tendency to be harder to train and more aggressive.  Is this
correct?

Answer

Pretty Head Hello Melanie.
I am a pretty new 'expert' to this site, cruising about and checking features, and come on the question pool, unanswered questions. I believe all questions need answers, or the tools to find answers, even if it is late.
To your question, I also have read similar words, but there is a misunderstanding happening here. Horseman know most horses when under extreme stress / fear / etc. can show white about the eye and I believe that is what the reference meant, originally. A sign for anyone to back off, come again another day. (if possible) No horse learns anything while 'mad or scared'!  Some Breeds show more white about eye than others, naturally, the Appaloosa is one, lots of Paint horses, others. The horse you are asking about is an individual, observation and testing by you or someone working for you is the only way to have any chance of predicting his/her trainability / disposition.
I believe the set of the eye, where it is ON a horses head, reflects more on the trainability in that the horse can see better. Conformation is the key. A TOP multi World Champion and Superhorse winner, USET winner/trainer,etc., etc., claims she never likes horses with 'almond' shaped eyes, she preferred a 'round' eye. So do I. Prettier !
Lots of "lore" about a horses eye but observation/challenge of the individual is the only final measure of trainability.
Hope I helped some.
I do love a nice BIG, SOFT, eye !
Take care Melanie. Great question !

Bill