Color is a factor of primary importance in the market value of raw tomatoes. J. N. Yeatman A. P. Sidwell K. N. Norris [ Food Technol.14, 16 ( 1960)] have developed an equation for color quality of raw tomatoes using purées of fresh fruit as specimens. The U. S. Department of Agriculture asked Hunter Associates Laboratory to design a photoelectric tristimulus instrument to measure this quality index directly. This has been done by modifying the Ohm’s law analog scales of the Hunter color difference meter [see R. S. Hunter , J. Opt. Soc. Am.48, 985 ( 1958)] to solve the tomato-color equation in four steps.