Yes to uranium for the bright yellow and yellow/green.
(I think something else may cause some shades of green, but yes to uranium being the typical cause of that.)
I think it is manganese which usually gives us the orange and red glow. (It's an m-word but I often forget which one. I think I have it correct this time.)
If you pull the brightest glowing marbles out and let your eyes get adjusted to the dark again, other marbles will then seem to come through relatively brightly. If you do that a few times, you can get down to levels of glow with different colors coming through. But they're more subtle. I don't know what causes all the different shades. It's just fun to notice sometimes.