A diagnostic method for color stability in an image printing system includes printing a test pattern onto output media; measuring, during the printing of the test pattern, an image of the test pattern on an image transfer surface using one or more image transfer surface sensors to obtain one or more image transfer surface signals; measuring a printed image of the test pattern on the output media using a printed image sensor to obtain a printed image signal; calculating correlation functions for the one or more image transfer surface signals and the printed image signal; and analyzing the correlation functions for the one or more image transfer surface signals and the printed image signal to identify a subsystem in the image printing system that causes variations in color within the plurality of prints of the test pattern.