Let me offer a thought.
What you call 'color' is technically referred to as 'timbre'. We consider a 'sound' made up of collections of individual audio domane energies that each in turn are made up of :
1 - Amplitudes - audio energy filling a frequency domain, such as a guitar string plucked. Such a signal has 'overtones', usually but not exclusively sequentially harmonically related energies as in 1st, 2nd, 3rd and so on. Non-harmonic information can be included by the author of the 'sound' as part of this design, like some energy as noise or posing some weird harmonic relationship (it is an art afterall).
2 - Phases - each of the individual Amplitudes or overtones maintains a physically and thus sonically unique relationship with every other overtone. Kind of a Mach's principle but in audio.
Thus is the timbre of the sound as the ear hears it. Change any of the individual overtone's amplitude or phase and you change its relationship to the 'ensemble', the 'sound' through any given time interval. In effect the whole is greater than the sum of the parts, it is a gestalt.
It in interesting that the measurement of Total Harmonic Distortion would suggest a good method of assessing performance relative to upsetting the Timbre of a sound in circuit.
The fact is that THD is not very useful, it does not tell you anything about the Timbre. Nothing about either the amplitudes or phases of the overtones, Nothing al all about what has been subtracted from the overtones. 0nly the aggregate has an amount. In theory it will tell you a circuit adds to a overtone set of energies but says nothing about the important issue of relationships of overtones.
So we know what 'color' is along with a whole bunch of descriptive terms for sound. May a better way to talk about is the 'color of the tambe", who knows.
Good luck in your pursuit of knowledge, it is commentable.
BarryThornton
