What do "cool white" and "warm white" mean?
The Color Correlated Temperature (CCT) is given in the description of most LED bulbs. The color (CCT) of the white bulbs ranges from a warm yellow (2700K) to a cool blue white (7000K).
By comparison, a typical incandescent bulb has a CCT of 2800K. A typical halogen is a bit higher, maybe 3500K. Daylight white is 4500K and a cool white fluorescent is 6000K or more.
The human eye adapts to background light so that even a daylight white bulb will look slightly blue in a room illuminated mainly with incandescent bulbs. Similarly, an incandescent bulb will look very yellow in midday sunlight.
For more information about lighting and color temperature, contact Pacific Lamp.