We have ample evidence that colors began to have special meanings a very long time ago, and that those meanings were clear to the entire population. One of the most famous edifices of antiquity, the Ziggurat of Ur, built between 2300 and 2180 B.C. in the Tigris-Euphrates Valley, consisted of four main stories. Nor have we absolute proof, right on the spot, of the meaning of the colors. Judging by the use of similar colors elsewhere, though, there can be no question of an accidental, or whimsical juxtaposing of colors. Those hues were selected for symbolical reasons.
Most colors have several meanings, but they are closely connected with each other.
Green may also be water, but it generally means hope, the color of spring, the renewal of life, feed for animals, and thus, food for humans. Green also means poison, because arsenic, known in most ancient times, is green, and so are many poisonous sulphates. In more recent times, many poisons were manufactured in green powder form, in order to differentiate them from flour or sugar. Green also symbolizes jealousy, and fear, both of them deadly poisonous emotions. Black is death, the underworld, mourning, desolation.