Abstract: A method and apparatus to enable countertyping a tint by formulating a theoretical mixture of base tints having known colorimetric parameters. The apparatus employs a filter colorimeter, normally used only to compare differences in tint samples, and iteratively to define additions to enable matching tints by gauging the result of adding base tints. However, the colorimeter according to the invention is defined in its response to known standard tints, and the iterative process is then conducted in the colorimetric domain specific to the particular colorimeter. The response curves of the colorimeter are maintained in data files used to modify calculations made respecting the effects of adding tints, the characteristics of the tints to be added also being stored in the data files. The apparatus can operate an automixer.