“Fit as a fiddle” plays on “fettle” – it’s an intentional malapropism. (Or at least, it was, before it became a cliche.)
Where do you go to hear people apply “pitch” to any colour apart from black?
“To ring the changes on” originally was an English folk custom of ringing bells, each one tuned to a note of the scale. Each bell ringer had a number, and the order of ringing went through every possible permutation of the ordering of the numbers.
12345
21345
23145
etc.
I may have missed the wooshing sound, but how many other colors do thick tarry substances come in? Pitch Black => Black as Pitch no?
Yes, as far as black goes, “pitch” is a good word. I have heard, yea with my very own ears, people use “pitch” to describe other colours, specifically red and white (not yet heard pitch green). I guess, pitch (not all that common a word in daily use) has transmorgified for some into something like “very, with respect to colour”
My all-time favorite was coined by Ringo Starr:
"Tomorrow never knows"