I had a blue eyed white that was absolutely determined to become a sorrel (in the high California desert!). I would go out to the barn during the hottest parts of the day and find her lying flat on her side, sunbathing!
She wore a bonnet mask for her ears and eyes, but wouldn't tolerate a sheet or anything around the lower face. If we tried to keep her in, she'd kick the boards in! So... she'd burn around the nose and lips, the flanks and even parts of her belly if we didn't keep her slathered in diaper rash cream. She wasn't white most of the summer, but the dirt that sticks to the cream works as sunblock, too.