Correlated Colour Temperature(CCT) defines the color appearance of a white LED. CCT is defined in degrees Kelvin.

When the color temperature is around 2700K, the light color is reddish, which gives warm feeling and stable atmosphere.

Moving to neutral white at around 4000K, there is no obvious visual psychological effect under this color tone, so it is called "neutral" color temperature.

When the color temperature at 5000K or more, the light and color become whiter, giving people a cool and clean feeling.