When I was growing up, we had two poodles, Rocco & Piper. Rocco was white and in the summer his skin used to turn from a light pink to black. Happened every year. Come winter, he'd revert back to rosy pink.
l to r: Uncle Bill, Piper, Darren, Rocco, Dad
Around here, when Spring comes, Emma turns from white to black too, but she gets it from rolling around in my flower beds behind the house! *sigh*