Picture: Wikimedia Commons This can be a variation with the purely natural brindle markings the thing is on Frenchies. Even so, the tiger brindle sample shows a lot more defined stripes. Typical brindle is more of a muddled mixture. Not all Merle Frenchies have these health problems, but “Double Merles” https://frenchbulldogtexas.com/french-bulldog-colors-and-patterns/