Experimenting with colour in art theory is a way to explore its influence over our emotions. Some colours can make you feel calm; others, irritated or restless. They can make you feel at ease, stimulate your creativity, or even make you feel hungry.
Studies into the psychology of colour suggest that certain reactions are part of our evolutionary process and tend to be universal. Differences arise from cultural and subjective influences. So, green is almost universally associated with nature, growth and harmony. Whereas white can be the colour of weddings in one culture and funerals in another.