Gather your materials!(: Mason Jar(s), Marble(s), and paint! Doesn't need to be glow in the dark, but it makes it more fun(:
Put some paint on a piece of foil or something so it doesn't soak through. Roll the marble in the paint, then put the marble in the jar, and roll it around.(: You might have to repeat it a couple of times to get enough in the jar. If you want more than one color, let it dry first. WITH THE CAP OFF. Trust me, I'm an idiot and screwed the cap on to let it dry.xD
Keep doing that with all the colors you want, then let it dry overnight.
Tadaaa!!! You're done(: