A set of colours aesthetically pleasant are described as in the language of human visual perception. As this encloses a subjective part, a psychophysical experiment carried out to estimate the perception of colour harmony combinations of paintings with the uniform colour of walls which they are hung. The experiment, that involved 38 observers, was based on colours built upon a specific colour flow. Participants asked to judge the colour harmony of combinations of of 7 selected paintings with backgrounds uniformly in 3 different ranges of colours—achromatic colours, derived from the global average colour of the considered and tones derived from the complementary of the average colour of the considered painting. Results demonstrate that the best colour harmony is when the average colour of paintings is used to colour background. The experiment presented in this paper shows that the white colour usually used for walls does not optimize the colour harmony.