Colors of trigrams
Connie Achilles found a very logical way to assign colors to trigrams. From bottom to top the lines have frequencies from low to high. For the "pigment" colors (yin lines) the RGB-spectrum, the lines are red-green-blue from bottom to top. For the "light' colors (yang lines) the CMYK-spectrum, the lines are cyan-magenta-yellow, from bottom to top. Pigments are usually made from "earth", like e.g. siena. The sons belong to earth, the daughters to heaven, together they are white, or rather colorless light.
So fire, which has the second line yin, is magenta. Or � because
it has the bottom and top lines yang, it is red + blue, and those two together
are magenta. Lake is yellow, because of the yin top line. Or it is red + green,
which is also yellow.
Hierarchy of symbols or archetypes
The ultimate is Wu Ji, the great void, usually depicted as an empty circle. After that comes Tai Ji, the symbol of yang and yin turning around and eternally alternating.
For the explanation of the colors: see the page by Connie Achilles. It seems it is not on the internet anymore, so I put it HERE.