Yeah, Green/Blue/Red coin. Gives you a support matching the color and all the supports are one's that are check-listed already for the gem.
If I recall there's a few gems that say they work but don't, and a few that work but don't say they work in the gem window. Like less than 2 or 3 interactions if I remember. Hopefully none of them are important.
One example is somewhat between where Behead support can work on slam zombies, but they can never strike so it doesn't actually do anything. Think there's some interactions with minion speed support as well that I don't remember.