Ever wonder why the same object can look different in various lighting? There are blue, white, yellow, red, and many other colors in the spectrum of every lamp. This is determined by the color rendition index, CRI, of that type of lamp. The higher the CRI, the more color the eye can see. Every type of light source has a different CRI which then makes whatever is being lit up look differently.
Even daylight has different CRI values. Depending on the time of day, what type of sky is present that day, and where the sun is positioned can even change how things look. A day with a clear blue sky will look different than the beautiful orange, pinks, and purples that exist sometimes at dusk. The CRI can change from 8000 Kelvins to 2600 Kelvins in a single day making the same object transform as the day goes on.
Different types of lamps (CFL, LED, Incandescent, etc.) with the same CRI can also have variance in the way they color things. A cool white fluorescent lamp has a reddish-yellow appearance while an incandescent fluorescent lamp has an orange color. Personally I have purchased a package of many lamps to have some looked bluer while others were more orange. This is probably rarer, but it can change the way things are seen in the light.
LED lights used to be blue. Technology is changing and you can now purchase an LED light with the full spectrum. This is done by putting the LED inside a color tube or container, or by changing the semiconductor materials used in the production process.
Finally, this not only affects how things are perceived by our eyes, but also changes how a photograph turns out. Not just the light being cast in the surrounding area, but also the lamp used for the flash can drastically change how a picture looks.
What other ways have you seen the CRI of a light change how things look?