I have a few pairs of Gray, Black, and Blue that I've bought from Stu over the years; even back when he lived in Pennsylvania.
I'd sort of agree with using the Black for some model CD players. The black is a little more "analog like". Question is...does Stu still have the supplies to make the Black? The Black also use to make a pretty good speaker cable for electrostatic speakers.
For most analog equipment though, like tuners, turntables, tape decks, the Gray is very fine for the $60 it now costs. Fine for some CD players that might be a litte laid back
The Gray also makes a mighty fine inexpensive digital cable. Wadia years ago use to include in the box, one of Stu's Gray cables as a digital cable, to go along with some of their early DAC's. You might find some old archived Stereophile Magazine articles on using the Gray for digital.
The cheap Blue were/are very fine for replacing OEM cables in inexpensive gear. In better more revealing gear you can hear a hint of grain in the sound. But for the +/- $30 he use to charge for them, no one should be complaining. He may not be able to make these anymore..?? You'll have to ask...