My stud was the same way. He wasn't partial to red anything and we'd find blankets, halters and ropes shredded or nipped in two if it was that particular color. Switched to blue and he was fine with it. He'd breed a chestnut mare, but really preferred greys. Wonky horse.... I miss him.
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LOVE the horse's paintings. How fun!
I know that horses see a few less colors than we do because they don't have the same number of cones in their eyes. Breezie won't paint with red. She doesn't seem to acknowledge it. At the most, she'll dab it on the canvas a couple times then drop the brush and look for a coherent color.