Yellow soles???

So today I noticed my 8 year old has yellow soles of his feet? Like, tinted yellow. He was just at the dr for a checkup and everything looked fine but I guess I never look at the bottom his feet. Could it be something bad? Hes super active and eats very well. Idk if I should call in or if they'll think I'm crazy lol sometimes he has a yellow tint and I mentioned that but they didnt see it, they said it was probably his skin tone. Hes Hispanic mixed so almost olive tones. They looked him up and down and said he looked normal toned to them. But his feet are VERY yellow. At least to me. Like I said, he seems very healthy. I'm all worried now though lol