We have several times had to call attention to individual differences among people as regards their attitude towards colours. It may be well now to discuss these differences more fully. Edward Bullough in an important series of experiments has shown that many individuals can be classified into types according to their usual way of regarding colours. In these experiments seventy different shades of colours were used, and thirty-five subjects (three of whom were women) were tested. The experiments took place in a dark room, artificial light being used in order to avoid the variations of daylight. The subject looked through a circular hole at the illuminated coloured paper, and was asked to state whether he liked or disliked the colour, and particularly to give his reasons for liking or disliking it. Now it is quite true that we are often quite unable to say why we like or dislike a colour, and it is probably true that no one is able to give all the reasons that help to determine the exact effect that a colour has upon him, for, as we saw, many sources of our feeling may be buried in experiences long since forgotten. But it seems fair to suppose that, in so far as reasons can be discovered by self- examination, those which are most influential in determining our preference will in the long run attract attention most readily and most frequently.
It was found that the reasons given showed that different aspects of colour appeal strongly to different people. These aspects of colour, or ways of regarding them, Bullough found to be four in number, illustrated by the following judgements actually given by some of the subjects: