I am no artist and this was a pretty impulsive idea, but I thought I'd write it down anyway :)

A gem series with red, orange, yellow, green, blue, and purple. Orange, green, and purple could be combo bases created from their respective IRL combo (red+yellow=orange.) There's also a lot of gem eye colors that could then have matching bases.

In my head, the bases are mostly solid colored but might have shiny effect to make them gem-like. All bases would have identical effects so the only difference is the color. My idea is more for the concept, though, so the exact appearance could differ.

Names Ideas:
Ruby, Garnet, Jasper (red)
Fire Opal, Jasper, Sunstone (orange)
Heliodor (yellow)
Emerald, Dioptase, Jade, Malachite, Peridot (green)
Sapphire, Celestite (blue)
Tanzanite, Amethyst (purple)

Like I said, just an impulsive thought that I wanted to write down. No worries if it isn't for you :)

Also I know a lot of people have made individual suggestions for bases matching some current applicators, and they're really cool so make sure to check those out!