Value

Represents a visual perception of Luminance - often judged relative to a similarly lit object

Lightness is a predictor of how illuminated a colour will appear to a standard observer, and is tied to colour perception

In practical terms, it represents how light or dark a colour is - e.g. orange has a higher value than navy blue or dark purple.

Black is lowest value, white is highest.

In design, favour colours with different values (especially when working with high chroma) - high Contrast lends itself to more pleasing design