As the metal heats, the color first appears as red and changes to orange, yellow, white, blue-white and then to deeper colors of blue. The temperature of the metal can be measured in degrees Kelvin, or absolute temperature. The appearance of the sun as it rises is approximately 1800 Kelvin. As it climbs in the sky, it changes from red to orange to yellow and to white at noon, when it reaches 5000 Kelvin. It reverses the scale as it sets.
Color temperature describes the warmth or coolness of a light source.
All CRI values are relative to sunlight which has a CRI of 100. Spectral Distribution Visible light is a small part of the entire electromagnetic spectrum. Radiant energy travels through space as electromagnetic waves. The human eye perceives wavelengths between 400 and 700 nm. Between 590 to 630 nm - orange From 630 and, to a bit above 700 nm, light appears red.