Real-time color segmentation can easily be performed on PCs equipped with inexpensive imaging hardware. An efficient colour-classifier implementation consists of a color look-up table (CLUT) followed by a binary median filter. The crucial part is the application-specific design process of the CLUT. The goal of our interactive classifier design tool is to quickly obtain a reliable CLUT from a training set of images. The tool is controlled via a graphical user interface. The function of the resulting classifier can be checked with previously saved test images.