A method that allows an objective description of microscopic surface changes of paint coatings was developed for the quality assurance of paint and cleaning agent's producers. Colorimetric and morphological features can be quantified by the method of digital color image analysis. The first step to apply this technique requires a systematic investigation of the color transformation properties with respect to the selected input/output devices used for digital imaging (flatbed scanner, CRT display). Next step is to develop a color management system. Therefore mathematical models of the color transformation processes were optimized and embedded in commercial color image analysis software. For an industrial application, such system allows the objective characterization and description of decorative quality of paint coatings after weathering. An extended version of this system is implemented successfully for quality control and certification of car washing stations and affiliated cleaning agents.