Ringo had patches of grey hair early in his life. Perhaps you heard about the grey patch in his hair, near his left temple? Well, he had half a grey eyebrow. He used to color it in with eyebrow pencil to make it look normal. He talks about this in the Beatles Monthly magazines.
He also said his beard would grow in half grey, so whenever he wore one he used to like to dye it to be all one color. Then he'd get sick of dying it and shave it all off.
Excellent question for the Ringo thread, Popaloptop.