The colour of light affects the spiritual and the physical.
The physical, we can say, is the body and all material things.
The spiritual aspect is the mind, thought, imagination and consciousness which you cannot see but which nobody doubts exists.
Yellow is the colour of the mind. It is the colour of the mind physically and in the unseen spiritual aspect.
It is an active colour.
Yellow has a shorter wavelength than red, which means it conserves energy more than red. But the energy it squanders stimulates mind things and thoughts.
Books, new ideas, humour, stimulating conversations, academic teaching, learning, reading, art works, architecture, concepts, all the skills of learning are yellow.
The effect yellow has on the body is to stimulate all the organs of the body to action. That also means the digestive organs, the bowels, the salivary glands, the bile ducts and the skin. All internal organs react to yellow; for example, the secretions of insulin are stimulated so it is helpful in diabetes and digestive disorders.
Yellow can be used where red is not indicated or is too violent – for example to give energy to someone who is already over stimulated or is suffering some malignancy or inflammation.
Yellow is an action colour. It is an energizer.
The yellow rays of the sun give life to the earth. A yellow room cheers. Yellow brightens the outlook on life because it peps up the energy level. Monks use saffron robes in the east because it is a mind colour and the mind is their gateway to God. We talk about the light of learning and enlightenment. Comic books show a yellow electric globe over the head to indicate that a character has a good idea.Catholic Saints are depicted with yellow halos. And we wallow in the golden glow of achievement or success.
Learn to colour your life with yellow. Like all colours of agitation, it should be used sparingly. Too much mental action, learning, study, academic knowledge is just as bad as too little. The Buddha taught that all things must be done in moderation.
There is a way in which yellow can be tempered to be less of a mind colour and more of an earthy colour, and that is to make orange. Orange is a very useful colour, having many attributes of red and many attributes of yellow. It combines physical action with mental action.