The principal aim of this study is to demonstrate the extended applicability of the experimental tool (GUI) used in the colour imaging manipulation experiment of gamut compression by applying it to the study of gamut extension. Unlike gamut compression, the gamut extension study mainly deals with pleasantness of observers. There has been very little published data about gamut extension so far. The results of the pilot gamut extension experiments in this study not only give worthwhile data but also suggest a methodology for using the observer experimental tool for future gamut extension research.