“But when two colours are similar, the experience of similarity should surely consist in noticing the similarity which there is between them.” ‒ ‒ But is a bluish green similar to a yellowish green or not? In certain cases we should say they are similar and in others that they are most dissimilar. Would it be correct to say that in the two cases we noticed different relations between them? Suppose I observed a process in which a bluish green gradually changed into a pure green, into a yellowish green, into yellow, and into orange. I say, “It only takes a short time from bluish green to yellowish green, because these colours are similar.” ‒ ‒ But mustn't you have had some experience of similarity to be able to say this? ‒ ‒ The experience may be this, of seeing the two colours and saying that they are both green. Or it may be this, of seeing a band whose colour changes from one end to the other in the way described, and having some one of the experiences which one may call noticing how close to each other bluish green and yellowish green are, compared to bluish green and orange.