Green pigments usually have a “PGXX” designation, where “PG” means “Pigment Green”, and the Xs are digits which correspond to a certain chemical substance (or range of similar substances). For example, PG7 is copper phthalocyanine, a bright blueish-green substance usually called phtalo green.
The list of available green pigments isn’t excessively large. Many green paints are, in fact, so-called “convenience mixtures” – pre-mixed shades of green, the purpose of which is to free the artist from the tedious task of mixing his or her favorite green again and again every day. Interestingly enough, you will not find a green paint consisting of a yellow and a blue pigment. All green mixtures are based on green pigments, to achieve the highest chroma possible. This is also why having a green paint on your palette is so useful.
Below, you will find the swatches of all the various greens that I have or had in my possession. Swatches have two areas, the upper one to demonstrate the range of tints (diluted paint), and the lower one to show the mass-tone (the paint taken straight from the tube without diluting or, in case of the pans, the thickest concentration I could get). On each swatch you will notice a black line – I made it to give the idea about the transparency of the paint.