Once again, this is for the people who beleive they're the same person. If they're not in your au, then that's fine.

So more back on my Sun/Moon theories(This one is for the people who beleive their the same person); Sun's rays would go into the head, which would explain where they go. But would the back-hook open to eject Moon's hat? And if so, that would explain why it's big on him to. It's so it can go back into Moon's back when becoming sun. But this doesn't explain the color changing. Is it like a specific paint that changes color depending on the amount of light?