Color Temperature or Correleted Color Temperature (CCT) is measured in Kelvin (K) and indicates whether a lamp has a warm or cool color appearance.
The incandescent lamps are considered warm light sources, because they have a low color temperature (2700K) and their color appearance is more the red/ orange/ yellow range.
In the other hand, the fluorescent lamps are considered cool light sources, because they have a high color temperature (>4000K) and their color appearance is in the blue range.