A method for controlling an illumination system comprises determining first drive settings for each of a plurality of colored light sources, the first drive settings generating an ON and an OFF time of the light sources; for each of the light sources of a first color and the light sources of a second color changing the first drive settings so that the ON time of the light sources of a selected one of the first and second color does not coincide with the ON time of the light sources of the other colors for at least a period of time, and during that period, measuring the peak luminance of the light sources; and for each of the light sources of the first and second color recalculating the drive settings, based on the measured peak luminance for the light sources of that color, so as to maintain a pre-determined color point.