A recent view of Jupiter through my telescope made me wonder, as it usually does, just what sort of weird chemicals must be floating around up there. All the ingredients are there, and the intense heat and pressure in the lower layers would be enough to drive most any reaction you could think of. The various colors of the clouds (yellow, brown, red) are a clue that there's plenty going on.
I've seen those colors before, and my organic chemist readers will know exactly where I mean: stuck to the top of the silica columns that I use to purify compounds. Side products in organic chemistry reactions can give you some intensely colored materials, which resemble the colors in Jupiter's clouds quite closely. (Early in his career, Carl Sagan coined the word "thiolins" for these colorful organic mixtures. To a chemist's ear, that makes it sound like sulfur is the most important component, which isn't necessarily true.)
Frankly, though, none of ever really characterize the stuff. We're just trying to get rid of it as fast as possible. Medicinal chemists know that there are mightly few maroon or chocolate-colored wonder drugs; most small organic molecules have no color at all. A few of them are yellow, but a faint yellow color that's usually a sign that you've got a small amount of something that's reallyyellow mixed in there.
OK, there are exceptions, like azulene, a small hydrocarbon which is a startling blue color. It's a useless compound to a medicinal chemist, but I've always been tempted to order some for my lab just so I can have one blue compound in the place. I'm not aware of any organic molecule that's green without the help of a metal like nickel or copper. There are a few honest purples, but they're usually weird anions, nothing that you'd keep around in a bottle.
The corollary to that is that the photos you see of keen-eyed researchers holding up Erlenmeyer flasks of green liquid are faked. It's food coloring. I've been in the lab when they come around for annual-report publicity shots, and they always want to dress things up. The same goes, in spades, for movies and TV shows. If anyone out there has a copy of Ebert's Little Movie Glossaryby Roger Ebert (1994), you'll see my contribution on page 59, the "Law of Colorful Chemicals." (That's not my current address in there, by the way.)
The oddest color I think I've seen was a fluorescent shocking pink compound that turned up in the lab next door when I was an undergraduate. This stuff hurt your eyes; it was dazzling, and completely unexpected. The guy who made it darn near dropped the flask.