We introduce a new technique to describe hue content in colour appearance. In contrast with classical colour matching, which implies visual equivalence of colour stimuli, partial colour matching means that two coloured stimuli may be different (do not match each other) but may have some hue in common. When comparing a pink and an orange stimulus a trichromatic observer can see some red hue in both. Alternatively, red and green, being complementary, do not even partially match as they have no common hue. Using a sample of twenty Munsell chips, we carried out an experiment asking observers to decide if a partial colour match exists for every pair of chips. A partial colour matching matrix was used to derive the set of component hues which the observer used in their decision making process. The results reinforce the classical notion of four unique hues. It must be said, however, that the results were obtained without resorting to verbal categorisation or knowledge of unique hues. This maybe crucial for making use of the technique in the examination of children and subjects with colour vision abnormalities.