The Color Rendering Index (CRI) is a rating system that measures the accuracy of how a light source makes specific colors look.
CRI tells us how accurately a light source displays specific colors. They are listed below.
If a light source displays these 14 colors perfectly the corresponding CRI would equal 100. If the light source did not display any color correctly its CRI would be 0 (zero).
The CRI index was created to help companies sell products. If a light source does not accurately display colors, the carpet that you purchased in the store may look completely different at home. A red shirt may look orange or pink. A white car may look grey or cream.
Do your plants care about CRI? Only if they are buying carpet, shirts, or cars.
Some horticulture lighting brands publish the CRI values. However, CRI value has little to do with lamp spectrum or its ability to grow plants.