actual acids are pretty much all clear i think
and with radioactivity, and with poison, all three of which are often conflated in the context of games
This is not an exhaustive list, but here are some thing that come up, plus a few of my own ideas:
- medieval Europeans associated snakes with temptation, evil, and poison, and often depicted snakes as green
- arsenite was once a very popular, vividly green pigment that turned out to be extremely poisonous
- radium was used for its green radioluminescent glow and famously poisoned the radium girls who worked in watch factories painting glowing dials
- human vomit resulting from poisoning is green due to bile
- Mr. Yuk is a fluorescent yellow-green symbol meant to warn children that something marked with him is poisonous. The study that created him found that children rated neon yellow/green as being the most unpleasant color