How light colour affects people

Light sets our body clock

Our daily rhythm of sleep and wakefulness is set largely by the light that reaches our eyes. Some cells in the eye are especially sensitive to blue-rich light. Getting this kind of light during the day tells the brain it is daytime; in the evening, dimmer and warmer light prepares the body for sleep.

This is why staying under bright, cool light in the evening can delay the release of the sleep hormone melatonin and make it harder to fall asleep.

Cool light: focus and energy

Cool and natural white light with strong blue tones supports alertness and concentration during the day. Offices, classrooms and gyms that should feel lively usually use light between 4000K and 6500K.

In spaces meant for relaxing, however, cool light can feel formal and cold, and uncomfortable over long periods.

Warm light: comfort and closeness

Warm white light (about 2700–3000K) recalls the setting sun; it relaxes people and makes a space feel welcoming. In restaurants, cafés and hotels it helps guests feel at ease and stay longer. At home it is the best light for the evening.

Light colour changes how a space feels

• Cool and natural white make a space look larger, cleaner and tidier.
• Warm light makes a space look smaller but cosier and more inviting.
• The same product looks a different colour under different light, so in sales areas light colour and colour rendering (Ra) must be considered together.

Eye comfort: flicker and glare

The quality of light matters as much as its colour. Flicker you cannot consciously see and bright light shining straight into the eyes can cause headaches, eye strain and poor concentration. Fixtures with good drivers and diffusers keep these effects to a minimum. Our LED buying guide explains how to spot them.

The right light for the purpose

People respond to light differently. If you have concerns about sleep or eye health, please speak to a specialist.