Ben is a rescue cat aged about 7. He has been with us for 6 years. He is black with only the odd white hair. When he lies in the sun, there is a reddish tinge to his fur unlike Ollie who is also black but his fur is pure black. Recently it seems as though Ben is developing red / rust coloured patches of fur. He eats only dried food - he will not eat anything else. Other than this change of colour, he seems healthy. Is this something to worry about or maybe it's part of the aging process? Does anyone have any experience of this?