...Winifred Nicholson, Devised a spectrum of hues and values entirely related to natural objects. Her scale underlies the fact that surface colours possess charachteristics apart from the hue, value and saturation (chroma), which have usually been held to define the parameters of colour as perceived.
John Gage, Colour and Cultur

Colour: Art and Science, Cambridge University Press, 1995

pg 184