Took me long enough.
There is a mind-bending pile of information on how the human race has produced green, down through history. Unlike most colors, green dyes and paints were usually of very different material, and there was little, if any, cross-use of pigments (unlike, say, madder being used as both a dye and a paint). So this is going to be a little more scattered than the other colors were.
The word green, in English, comes from a word in Old English meaning "to grow", which makes sense, considering the whole chlorophyll situation. (Incidentally, chlorophyll gets it's green from magnesium in the chemical structure. It's green on a molecular level, which is kind of cool. Oh, yes it is. Keep complaining and I'll start in on porphyrin rings and thylakoid membranes.)
Green has given painters fits pretty much from day one. Not only because it's hard to find a pigment that doesn't fade, darken, or generally turn to crap, but also because, duh, if you wanna paint nature, you're gonna need a bunch of green. To the left is the painting "The Arnolfini Marriage" by Jan VanEyk. It's one of the most famous paintings in history, from a conservation point of view; that green dress has remained green since 1434. VanEyk used vergigris, a form of copper (you know how copper turns blue-green when it corrodes? That stuff.) Depending on the exact chemical composition (the different gunk that was in the air when the copper corroded), it's not terribly light-fast and will often fade to brown. All those older landscape paintings? The ones that look so dismal? They probably weren't like that to start. They were likely painted green and have turned to brown over time. In the 1700s, they found a way to make verdigris a bit more light-fast as an oil paint (though not in other forms), and it was an extremely popular color for house paint, mostly interior. I've you've ever been to Mount Vernon, the home of George Washington, you've seen verdigris paint; that unholy bright green in the dining room was made from a historic recipe. I've been there, and let me tell you, that paint is ungodly bright. The tour guide was going on about how it looks better in candle light, but the real truth appears to be that they really DID like screaming bright colors in the early 1800s.
The other, most common form of green was "Scheele's Green". Invented in 1775, it's a crazy combination of copper, sulfur, and arsenic that is horrendously toxic. Scheele himself knew BEFORE THE START OF MANUFACTURE that it was poisonous, but went ahead with sales anyway, knowing he'd make a fortune off it. He did. Even though everyone knew it off-gassed arsenic like crazy, it wasn't made illegal for over a century, and only disappeared when synthetic greens were developed in the late 1800s. This is the stuff that is implicated in the death of Napoleon; no one's quite sure how the Little General died, but recent tests have shown he had really high arsenic levels in his body at time of death; it's also been proven he had wallpaper with Scheele's green on it, in his bedroom. (Homicide? Accident? More can be found here.) In addition to the toxicity, the green would darken when exposed to any kind of sulfur, either in paint, or in the atmosphere itself - and burning coal, which was THE power source of that era, puts LOTS of sulfur into the atmosphere.
Malachite is the last of the paint pigments, and another mineral, a form of corroded copper, like verdigris. Unlike verdigris, though, it's not very toxic and fairly stable. The drawbacks? The color's never the same twice, due to major variations in the stone. It doesn't do well in acidic environments or near acidic paints. And it has to be ground coarsely or the color gets lost. Back in the day, ground malachite was used by the ancient Egyptians, both as a paint and as a cosmetic. They wore it as eye shadow. Imagine getting stone grit in your eyes by accident when the brush slipped. Ow.
If painting was rough, dyeing was worse. Green was created through most of history as a two-part dye process; blue and yellow. Which of course takes twice as long, is about twice as expensive, and it's guranteed you'll never match the color from one batch to the next. The most popular combo in Europe was indigo (blue) and weld (yellow) to make green. In the years since, the weld has faded and left us with a whole bunch of blue fabrics - especially tapestries - that are considered very artistic (William Morris copied the scheme, thinking it was artful and subtle) but in fact were originally as literal and true-to-life as most other artwork, then and now.
The first true green dye, or one-pot dye as they're known, was Chinese Green, or Lo Kao. It's made from two species of buckthorn, using their bark. The bark is stewed for several days, then fabric is thrown into the stewpot and allowed to soak up the colorant. Then the fabric is hung up in the sun, and the light turns the muddy brown to green. Then the green is washed from the fabric and allowed to dry into a goo that was exported in huge amounts (from China) and sold for exorbitant amounts, mostly in Europe. Lo Kao didn't hit Europe until 1845, and by the end of the century, synthetic greens had replaced it for economic reasons. But for that fifty years, people paid through the nose for that green goo.
A quick flip through my organic dye books shows that even now, with the world at our fingertips (so to speak), green dye from traditional sources isn't an easy thing. There is nothing close to a true, bright green, and the olive greens produced by some plants requires an iron 'modifier' bath, which darkens the pigment and often damages the fibers.
There is a green food colorant. It's one of the early coal-tar colors, like most other food colors. Known as FD&C Green 4, Green S, or E142, it is illegal in Canada, the US, Japan, and parts of Europe. It's still available here as a dye, however. Chemically, it is a relative of tartrazine (see yellow discussion), and is implicated in hyperactivity, allergic reactions, and some forms of cancer. Yum yum.
Well, this is quite long enough. Even though I haven't begun to really get into the details. Definitely gonna have to return to this subject. But for now, I will leave you a photo of one of my favorite green things: