I heard that about dapples too, but I thought it only applied to non gray horses. As far as them being healthy or going through a color change in the spring and fall.
At closer examination, Gracie does have some red/brown hairs mixed in her coat especially low on the hinquarters, gaskins and hocks. Never paid that much attention I guess...LOL. I did pull out her registration papers that have a photo of her as a baby, she was a black and white paint baby.
Color genetics are beyond my comprehension! :)
I DON'T LEAD 'EM AND FEED 'EM, I RIDE 'EM AND SLIDE 'EM.