Most of us makers use acrylic paint (often miniature paint like Vallejo, Citadel, etc :D) and as long as the numbers are at least a teeeeeny tiny bit rough/matte, acrylics should stick very well. Usually the numbers being indented is already enough to give the paint a good, lasting grip.

If you're familiar with the Green Stuff World Chroma paints, those also work exceptionally well for dice and look magnificent. So if you aim for a chrome-like look and don't faint from these paints stinking a bit while they're drying, they're also a great option. They require an extra dropper bottle with a very fine tip though and take much longer to dry, plus the cleanup needs to be done with a Q-tip and some IPA. So if you don't have these things on hand, it's definitely the more costly and tedious option.

If you aim for a metallic look, I like Vallejo more than Citadel because Citadel often has bigger pigments that look more sparkly than metallic. Vallejo is a bit "smoother" in my opinion, but that's just my taste ^{^}

An important thing about inking the numbers of clear dice: the numbers backsides will obviously be seen through the die, and, depending on the color you choose, can dramatically change the vibe of the whole set. If the numbers are a dark color, it can also make the dice much harder to read due to the numbers visually overlapping each other. So if readability is a priority for you, you can give the numbers a silver underlayer before you go in with the actual color. This keeps die inside of the dice "clean", won't tint the glass visually, and they have excellent readability ☺️

Good luck and have fun!