Color Temperature and Color Rendering Index
To choose the right color fluorescent lamp for a specific application, consider two things: (1) Color Temperature, and (2) Color Rendering Index.
Color Temperature is expressed in degrees Kelvin (K). For example, noon daylight is about 5500 degrees Kelvin – the same as the full spectrum Vita-Lite. Fluorescent lamps with lower color temperatures look red; fluorescents with higher color temperatures look blue. This makes sense if you imagine an iron bar being heated. First it gets "red hot." Then, as the temperature increases, it becomes "white hot" and finally, "blue white" hot.
Color Rendering Index (CRI) is a numerical system that rates the "color rendering" ability of fluroescent light in comparison with natural daylight, which has a CRI of 100. This means that a lamp with a CRI of 91 shows colors more naturally than a lamp with a CRI of 62. Most standard "cool white" fluorescent bulbs range 60 to 75 CRI. This rating method is recognized by the Illuminating Engineering Society (IES) and the Commission International de L'Eclairage (CIE).