Hitherto, methods for visual assessment of colour appearance have not been developed for use in the study of rooms, We seek a practical method that allows one or two observers to characterize a room by identifying the perceived colours, Verbal descriptions are necessary, but lack precision. A magnitude estimation method may enable a more precise location in colour space. However; the need of a group of well-trained observers makes it impractical for room studies. A method involving matches between reference colour samples and the perceived room colours would be ideal. But, reference colour samples require a standard illumination; otherwise, the sample changes colour due to different room light. Hence, a method involving a colour reference box was developed. The colour reference box with its standard source of illumination provides a reference situation, where colour samples can be visually compared with the colours of the room. The study presented is an evaluation of this colour reference box. The crucial problem is that the same color sample in the box is perceived differently as the observer adapts to various lighting conditions, The aim of the study, was to investigate if these different perceptions of the samples could be described and controlled In the study, 18 observers were asked to visually assess the hue of 15-66 samples, and mark its place in the NCS hue circle. The assessment of the samples was made in two different room lights: incandescent light and stimulated daylight. The result of the study showed a clear tendency for the samples, perceived in the box, to shift colour in simulated daylight compared to incandescent light, It was concluded that the problem with the observer＇s adaptation to the room light can be described and controlled, although complementary studies are needed to quantify the adaptation effect with more accuracy, and to investigate differences in nuance. Thus, it seems that the colour reference bm can be used to visually evaluate and describe rite differences in colour appearance in different rooms. (C) 2000 John Wiley & Sons, Inc.