Chroma
The colourfulness of an area judged relative to the brightness of a similarly lit white, a perceptually defined counterpart to saturation.
Measured in
C* (CIELAB)
In depth
Chroma differs from saturation in its reference: saturation is colourfulness relative to the area's own brightness, chroma relative to a white reference in the same conditions. The distinction matters in colour science and in the CIELAB model, where chroma and hue together describe a colour's position independently of its lightness.
Examples in practice
A dark navy and a bright sky blue can share the same hue while differing greatly in both chroma and lightness.