It is known that one and the same interior colouring will appear different in rooms with windows facing north or facing south, but it is not known how natural daylight from these two compass points affects perceived colour and the ways in which colour is experienced. The objective is to describe the perceived colours to be expected in rooms with sunlight and diffused light, and thus develop a tool for colour design. Two empirical investigations provide the basis for six attached papers. The model is exploratory with a qualitative character. One hundred and ninety-one studies were carried out with 79 observers in full-scale rooms, with double-glazed transparent room windows facing north or south. The NCS colour sample collection and colour terminology were used, with three yellow, red, blue and green hues in two nuances: whitish 1010 and more chromatic 1030. The walls were painted in a total of 23 selected inherent colours with each colour observed in up to 10 studies. Colour matching was achieved using a colour reference box and results were analysed with the aid of the terms inherent colour and identity colour. The colour reference box was tested in a separate study to investigate any methodological problems. Room character was described using semantic differentials, and data was processed using the SPSS statistics program. Verbal description using own words was applied in a descriptive and reflecting method to find sensory differences and precise, yet ordinary descriptions. Colour differences between rooms were assessed using verbal description of hue and nuance, and a supplementary method with specified colour samples. Emotional impressions of colour and rooms were assessed using a method describing primary emotions and the results were compared with results from another study using small colour samples. The colouring that enhanced or neutralised room light situation was compared as regards emotional impression and thereafter compared with results from another study. Daylight from the different compass points caused a clear shift in hue and nuance. The perceived colour was consistently more chromatic and more blackish than the inherent colour used. Nuance 1010 shifted more in chromaticness than nuance, while 1030 instead increased most in chromaticness. Even minor colour differences resulted in major differences in colour experience. The north-facing room in yellowish colours shifted towards reduced yellowishness in both hue and chromaticness. Indications were that north-facing rooms in reddish blue become more reddish than south-facing rooms. / QC 20100716