If the color is different than it was before, than I would say it's not normal. But if it's always been that color, than I don't see a problem. But I must ask, are we looking at the inside of his ear? It's really hard to tell which part from the picture.
If it helps, I have a black cat who has one ear that is getting lighter on the inside. The Vet said he probably has Vitiligo and isn't worried about it at all.