Correlated Color Temperature (CCT)
CCT is what is used to describe the color appearance of a white light source. It tell consumers if the light source comes off more yellowy gold or more blue. Light sources are described as warm (yellow) and cool (blue) in design, but they are assigned an actual number in Kelvin to describe the color for consumers. The Kelvin number refers to the appearance of the theoretical black body heated to high temperatures. As the black body gets hotter it will go from red to orange, then yellow, white and lastly blue.
Color Rendering Index (CRI)
The CRI is what indicates how well a light source renders colors. It is based on a scale from 0 to 100, when compared to a reference light source of a similar color temperature. The test involves measuring the extent to which a series of eight standardized color samples differ when illuminated under a given light source. The average shift in the eight color samples is then reported as Ra or CRI. This measurement is useful to know how other colored objects in the room will appear under the light, and is useful with paint colors and paintings.