T-tests indicated that black was judged significantly heavier than the modulus assigned to white. Apparent weight is a decreasing non-linear function of value. Value and chroma are the major determinants of colour weight. Apparent weight is a decreasing function of value and an increasing function of chroma. These results support the earlier qualitative findings that “dark” colours appear heavier than “light” colours, while providing quantitative meaning to the terms dark and light. The reason that colours appear to have different weights is not clear. Bullough (1907) first offered the reasonable suggestion that the apparent density of colours determines their apparent weight just as the actual density of objects determines their physical weight. Colour weight would then be another example of a synesthetic interaction between sense modalities, in this case between vision and kinesthesis (see Marks, 1975). According to this scheme. hue, value. and chroma would interact to determine colour density; then colour density would determine colour weight by a process of synesthesia. An appropriate test of this model would involve sensory scaling of the various attributes of colour. (Alexander & Shansky, 1976)