A two dimensional color pattern which at each point has a definite and unique color value is reproduced on a measurement surface by way of a computer controlled display device for the optical marking of a target region on the measurement surface captured by a color measuring device. The color measuring device is aimed at the measurement surface and the color value of the target region captured by the color measuring device is measured. The coordinates of the target region on the measurement surface are calculated from the measured color value and an optical marker which visually indicates the location of the target region on the measurement surface is reproduced at that location on the measurement surface as defined by the calculated coordinates of the target region. Alignment of the color measurement device is simplified and made possible without the need for laser pointers or cameras.