1. Colour Temperature What is Colour Temperature? Colour Temperature is the measurement of a light source’s colour relative to an ideal light source. The unit of measurement for colour temperature is Kelvin, measured on a scale from 1,000 to 10,000. Daylight colour temperature is around 5,800 K, and the International Electrotechnical Commission (IEC) requires the colour temperature of surgical lights to be within the 3,000 – 6,700 K range. These colours provide the surgeon wi