The five elements as a palette
Wood, fire, earth, metal and water are five moods rather than five substances, and they are the vocabulary feng shui uses for balancing a room. Nine palettes below take them, and the Western stone tradition alongside them, and put them in gemstones.
They are the planets
In Chinese astronomy the five phases name the five visible planets: Jupiter the wood star, Mars the fire star, Saturn the earth star, Venus the metal star, Mercury the water star. Feng shui and astrology were not joined up later. They were the same vocabulary from the start.
The generating cycle
Water feeds wood, wood feeds fire, fire makes earth, earth yields metal, metal carries water. Two neighbours in that ring sit together easily, which is why a green and blue room works and a green and white one takes more care.
The controlling cycle
Water puts out fire, fire melts metal, metal cuts wood, wood breaks earth, earth dams water. Opposites in that ring are the pairings the tradition uses deliberately, to check an excess rather than to decorate.
How to use it without believing anything
Take it as a palette system. Pick one phase to lead, one neighbour to support it, and a touch of a third for contrast. That is a competent colour scheme by any modern method, arrived at through a much older door.