Effects of objects and light colours on emotions, mood, performance and health: a comprehensive approach.

Colours and lights have an influence on humans, mood and performance. In an indoor environment, walls and furniture colours affect the perception of the space and induce different emotions and psychological states. In the scientific literature several experiments have been addressed to study color preferences and emotional effects, also looking at different applications. Despite different adopted methods and visual tasks, findings are in quite agreement in asserting that "cool colours" as blue and green are relaxing, calming and peaceful, whereas "warm colours" as red and yellow result activating and arousing. On the other side "neutral colours" have less impact on emotions. As it is well known, white light emitted by lamps and luminaires is characterized by a colour tone, expressed by means of the correlated colour temperature(CCT). All experimental researches performed on circadian effects of light demonstrate that cool light, rich in short wavelengths, has a greater effect in terms of melatonin suppression rather than warm light, assuming the same illuminance value at the eye's level. CCT is not a synthetic parameter able to accurately quantify melatonin suppression, for example it roughly indicates that when very high values are attained, corresponding to a bluish white, circadian stimulus is high as well, once fixed the illuminance values. On the contrary warm light, characterized by low CCT values and corresponding to a reddish white has a lower impact, all other conditions being equal. Furthermore, researches confirmed that blue enriched light, i.e. light with a great amount of short‐wavelength radiations and CCT greater than 10000K has a positive effect both on seasonal affective disorder (bright light reduces SAD symptoms) and on cognitive performance in educational and office environments, stimulating attention and alertness. As a consequence of the above reported statements, some contradictions seem to appear: in order to obtain relaxing environments cool colours for furniture are recommended, whereas red objects or walls can induce arousal or sense of danger or of alert. At the same time, warmer lights (i.e. reddish lights) are more relaxing and cooler lights (bluish) have a greater effect on melatonin suppression and alertness. As the colour of light is concerned, other parameters have an impact on environmental perception, as illuminances, as well as for the objects colours, not only hue, but also chroma and value are involved. In order to better understand and overcome these contradictions, we first provide a critical analysis of the current literature and present a preliminary analysis of comparisons between different spectral irradiances at the eye, troughout combined effects of light sources SPDs and objects spectral reflectances. This could be a first step of a wider research aimed to provide advices for interior and lighting designers on proper colour choices of either light and furniture for different applications.