One of the instrumental color systems is the CIEXYZ system and a second is the Judd-Hunter Lab solid . The latter represents a color solid, where L = lightness or darkness , +a = redness, -a = greenness. +b = yellowness and -b = blueness. A third scale is known as the CIELAB system with parameters
L* a* b* . A fourth scale is the CIELCH system with parameters L* C* H*.