In cartoons, etc., acid is generally shown as vividly green, as in this scene from the Simpsons:
We even have the colour "acid green".
But when I used to use acids in chemistry class, they weren't bright poisonous green. They were mostly colourless, as, for example, this picture of sulfuric acid from Wikipedia:
So where does this idea of green acid come from? Are there acids which are actually green? Or perhaps acids are green when highly concentrated?