Colour temperature defines the appearance of a light source, from cool through to warm. It is referred to by its Correlated Colour Temperature, CCT and is rated in degrees Kelvin (K). Warm sources have lower values such as 2,700K compared with cool sources, typically 4,500K and above.
Warm LEDs are typically used where a relaxed atmosphere is needed, such as hotels, restaurants and domestic environments.
A cool appearance is often preferred for commercial locations such as offices and factories. In particular water features, glass and stainless steel often respond better to a whiter light source.