Invented in 1666 by Isaac Newton, we commonly use the colour wheel as a map of the colour spectrum to show us the relationships between different colours. The basic colour wheel is divided by hue and temperature, further classified by primary, secondary, and tertiary colours. More complex colour wheels incorporate tints, tones, and shades—created by adding white, grey, and black, respectively, to a base hue. Alongside hue, colours contain two other components: saturation, denoting vividity, and value, referring to brightness. Our basic understanding of colour associations centre around hue, however it is widely accepted that saturation, temperature, and value tend to have a greater influence on emotion.

Colours induce biological reactions that differ depending on their temperature, saturation, and value. Cool colours decrease arousal, promoting relaxation; warm colours increase arousal, stimulating excitement. These responses are further influenced by saturation and value—thus, a high value, low saturation blue is likely more relaxing than one with high saturation. Outside of experience, culture, and context, our biological reactions to colours sway our conscious and subconscious associations. For example, as red increases arousal—and with it heart rate and adrenaline—we tend to associate it with feelings of excitement, passion, and anxiety.