Abstract: Theme colors of oil painting represent the colorful keynote in the painting.In this paper we present a method for extracting theme colors from oil painting images.First, we predefine the number of main hues based on the color harmony type, and match the hue histogram with color harmony type.Second, we divide the hue ring into several segments with which the main hues can be detected.We assign pixels fallen into the hue segments with detected main hue values and calculate their saturation histograms from which the main saturations can be extracted.We further divide pixels associated with main saturations into subgroups and extract the main lightness from their histograms in the same manner.The candidates of theme colors are then composed by the components of the main hues, main saturations and main lightness and the theme colors are selected by use of Euclid distance in HSL space.Our method has the advantage over some of existing methods in preserving colors presented in a small number of pixels but visually significant.