Embodiments of the invention relate to the determination of the colour of a colour sample from an image of the colour sample. In one embodiment a colour sample capture card is provided having printed thereon colour samples of known colour (for example, XYZ tri-stimulus values). An image of the test colour sample is then captured using domestically available equipment, such as a consumer digital camera or camera-equipped mobile telephone, the image also containing the colour sample capture card. In one embodiment the image is then transmitted to a remote colour determination service for colour sample colour determination. Regression analysis is then performed using the RGB colour samples in the image and known XYZ colours thereof to characterise the colour capture response of the image capture device. Having characterised the image capture device the XYZ colour of the unknown colour sample can be determined from the RGB colour thereof in the image. A clustering algorithm is employed to identify if there is more than one colour in the unknown colour sample.