The color of leaves depend strongly on pigments present. Knowing how much chlorophyll and carotenoid is contained helps to estimate the leaf color. In autumn when it starts to get cold, foliage trees stop making chlorophyll. Instead, those plants break down chlorophyll into smaller molecules. As chlorophyll goes away, other pigments start to show their colors. Anthocyanins are plant pigments that are mainly made in fall, not all trees can make anthocyanin.
The three spectral power distribution curves shown below characterize typical colors of green, yellow and red American sweetgum (Liquidambar styraciflua) leaves.
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A unique hue is defined as a color which an observer perceives as a pure, without any admixture of another color. If we take red as example than there are pure red hues and hues that contain either yellow or blue. In the following the spectral reflectance curves of 6 red samples of the CES color set used in the IES TM-30-15 procedure are compared.

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By adding cyan and amber to red, green and blue LEDs the color gamut of a spot is considerably extended. To test conspicuity of chromatic light a chromatic patch was projected on a wall and was compared to an achromatic one. Below are the profiles for seven stimuli that demonstrate equal conspicuity measures.