the viscous oil is light to very dark green to dark red in colour depending on the thickness of the observed sample. the oil appears green in thin layers and red in thick layers, an optical phenomenon called dichromatism. pumpkin oil is one of the substances with the strongest dichromatism. its kreft's dichromaticity index is -44. when used together with yoghurt, the oil turns bright green and is sometimes referred to as "green-gold".