There is not a lot of hard evidence that colour can exert specific physiological effect that can be used therapeutically. Colours certainly do evoke affective response, and have some influence on a person's emotions, just as one's emotions are evoked by other aesthetic aspects of the environment, for instance by sounds, perfumes, shapes and textures ; and while each of these might have some therapeutic effect there is a good likelihood that when all these are appropriately 'tuned' and combined with coloured lighting, the holistic effect may be strong enough to trigger a powerful psychosomatic chain reaction.

One of the most impressive and successful experiments with coloured lighting was conducted in the Sunfield Homes for mentally handicaped children at Hagley, Worcestershire. A swimming pool with blue and orange-pink lighting was constructed in 1967. When the children entered the water they saw their own bodies illuminated in brilliant colour. Then, some of them realised for the first time that they had limbs. Spastic children, who were tensed up, opened out and blossomed in the pink light, whereas the hyperactive children were calmed and relaxed in the blue light. Michael Wilson was one of the founders of the establishment, which is at present run by Ralph Brocklebank.