What Causes Dark Yellow Patches On Face And Ears After Sunburn?

We went to Clearwater Beach, Fl a few days ago for vacation. We spent the day at the beach two days ago. My 14 year old son has Gilbert's syndrome. I noticed yesterday morning when he got up his skin was sunburn but had huges patches of yellow. It is dark yellow patches that are flat. These are not blisters. Just patches of dark yellow all over his face and ears. They are no where else on his bady. It is only on the areas that he was sunburmed the most. His eye have been quite yellow for about two weeks now as well which usaully comes and goes. Thought by making him expose himself to the sun that it would go away but it hasn't. His skin however was not yellow prior to the sunburn. It really looks rather weird. I have never seen anything like this in my entire 45 years of life.