I’m not knowlegeable enough myself to assert what "the rule" is. I’ve had silver cables that did lean toward the bright side, silver cables that were neutral and one that was on the warm side. None were power cords, however. Generally, I shy away from anything that would shift the system as a whole toward brightness.
I just bought and posted about Darwin Natural 2 silver ICs. They are notably transparent but not bright. And If I hadn’t just committed to a power cable upgrade, I would’ve auditioned Darwin’s ac offerings. In fact, if I had the $, I’d try an entire loom of Darwin but that’s not doable at present.
As mentiomed, The Cable Co. doesn't carry all brands.