A major part of the mind–body problem is to explain why a given set of physical processes should give rise to perceptual qualities of one sort rather than another. Colour hues are the usual example considered here, and there is a lively debate as to whether the results of colour vision science can provide convincing explanations of why colours actually look the way they do. The internal phenomenological structure of colours is considered here in some detail, and a comparison is drawn with sounds and their synthesis. This paper examines the type of explanation that is needed, and it is concluded that it does not have to be reductive to be effective. What needs to be explained more than anything is why inverted hue scenarios are more intuitive than other sensory inversions: and the issue of physicalism versus dualism is argued to be of only marginal relevance.