It is a recognized fact, that the relative surface coverage of the colors has a great influence on the harmony content. It is an open question that, in a composition, what is the optimum ratio between the surface area coverage of the colors, for maximum harmony content of the color pairs, selected for the composition. Various theories on color harmony already tried to answer this question, based on two substantially different principles. One is built on the mechanism of color vision, while the other one founded on statistical test results. The first approach was already proven not valid; but the second one was not proven right either due to the lack of available data. Our experiments aim is to fill this gap by using 324 compositions with different color coverage, to investigate its relation to harmony content. The statistical results were summarized in graphs as well as formulated in mathematical equations. The results show that the prime factor in the measure of harmony content is the relative surface coverage of the highly saturated colors. In most cases however the 50-50% ratio of color coverage leads to maximum harmony content in a composition. (C) 2013 Wiley Periodicals, Inc.