My first thought when I read your first post was as yours...Huh???
Then I got to thinking. Here the mahogany bay mare has a black/red halter. Paint gelding with blue eyes has black/blue. Soft bay mare came with purple, that just happens to match the trim on her inherited blanket. I guess I have fallen victim to the My Little Pony color ensemble thing after all.
I'd get a white halter that would not do anything to take attention away from that very pretty face!!! I love looking at those horses.