Disk color mixture, known since antiquity, represents a special kind of additive color mixture where the stimuli do not represent direct lights from light sources but light reflected from objects. Its complete elucidation took centuries, requiring means to measure reflectance properties and spectral powers of lights. Explanations of the cause of the mixture, the fact that perceptions are not instantaneous but take a certain amount of time were offered in the late 17th and early 18th centuries. The speed of disk rotation required to obtain additive fusion of reflected lights was determined in 1765. For a time in the second half of the 19th century disk mixture was the only means of establishing color matching equations and quantitatively defining color stimuli. The fact that its results neither agree with Newtonian predictions of spectral light mixture nor with the results of pigment mixture produced endless confusion in scientific and artistic circles in the Enlightenment. Today, there is no practical application of disk color mixture left and it has become a curiosity. (C) 2010 Wiley Periodicals, Inc. Col Res Appl. 35, 110-121, 2010: Published online 7 January 2010 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20566