Why is green the colour of envy?

When you envy someone, you are basically jealous of that person. Let me illustrate jealousy by the following two simple examples:

a. My friend comes to school in a car and I have to use my fucking legs.
b. Yours is so long.

I guess you got the idea. Now, ages back, when intelligent folks like me were busy creating the theorems of geometry or laying down voluptuous women, they were the dumb ones who came up with their own theories. For those, who believe in ancient Greeks more than me, here is their funda:

In the ancient Greek theory of medicine, which long governed medical treatment, it was believed that an imbalance of certain “humors” produced one’s physical symptoms. Jealousy was considered to result in an excess of bile, which would give a pale-greenish cast to the skin. (source)

I however think otherwise. Green represents the plants, the leaves, algae and all those chlorophyll containing organic things, right (ignore Pakistan for the time being)? Now where else is greenery found besides Earth? So, every other planet, satellite, asteroid or any other piece of shit floating in the universe is envious of earth because of the fact that it is the only place where one can find green things. Green therefore is the reason for the ‘universal’ jealousy! And green therefore should be the color of envy.

Having said that, did Pak intentionally go for a green coloured flag? Who was Alan Greenspan jealous of?  When you are jealous of someone on the face, and are still grinning from outside, should the act be called greening instead? Are those who are available, jealous of those who are busy (ref:gtalk)?