"In my opinion, the semantic development has passed through varna, "colour", in the sense of "one in a spectrum", with the spectrum of colours serving as a metaphor for other spectrums, e.g. varnamala, literally "garland of colours", meaning "garland of sounds", "sound spectrum", "alphabet". Society too is a spectrum, viz. a spectrum of functions or varnas."
January 1, 1970
https://en.wikiquote.org/wiki/Varna_(Hinduism)