Strange question-looking for your ideas

Very random, but here it goes. OK, so I noticed that DS (16 months) has a slight tan on his arms all the way to just above his knuckles. From his knuckles to his fingertips is whiter. I thought today that this is exactly the point where his bathing suit cuts across his hand. He has the long sleeve rashguard from lands end. I thouht maybe it blocked the rays from iving him a burn, but he still got some color but that doesn't make sense because his fingers are even whiter when they should be darker (I don't put sunblock on his hands.) My dad thinks it is the blue coloring from his rashguard (He does not look blue lol). So if you got this far, thanks, lol, now I'd love to hear some ideas of what's going on. Thanks!

Re: Strange question-looking for your ideas

Any ideas?