Kaykay - i've been present at numerous shows, but only shown at one so far - this is my first year!
I am FULL of questions and one of them, weeks before the show, was exactly this question - where should I enter my horses that are appy, but LOOK solid?? I had e-mailed the secretary and asked a few other people handling the show, sent photo's or description, and I was told numerous times to "enter the horse as they appear" and that if the steward feels there was a mistake, they will let you know. So, I entered my registered appy filly that is one solid color, in the solid class - no problem. And I had my white appaloosa stallion entered in solid, he would have done much better in that class but at the last minute the steward made note that he could just barely see a difference in skin color and said to transfer him into multi - if my stallion would have had one more week to grow out his hair, his skin color wouldn't have been seen and the steward would have kept him in solid - regardless of registered pattern.
Obviously if the appy has noticable spots or blankets, it isn't solid - but if you have a characteristic that is solid bay, or solid sorrel, or solid black...why put a solid colored horse into multi?
I am just going by what I was told here - not opinion =)