IPA: /ˈsʌbtoʊn/
KK: /sʌbˈtoʊn/
A secondary or lesser tone in sound or color.
The artist used a subtone to create depth in the painting.
Subtone → It is formed from "sub-" (meaning under) and "tonus" (from Latin, meaning tone or sound). The word "subtone" refers to a tone that is lower or beneath the main tone.
Think of a tone that is 'under' ('sub-') the main sound ('tonus') — that's what a subtone is.