Originally Posted by Q.G.
Green never contains yellow.
The impression of green you get when mixing blue and yellow paints is because green light is not absorbed by those paints.
It's green, because it does not contain yellow (and blue, etc.) anymore.
Yes, there is a whole book out on watercolor and mixing of colors that's titled Blue and Yellow Don't Make Green where the author (a guy named Wilcox IIRC) explains that phenomenon.