I prefer spelling it with an ‘e’ so I always do that (probably because my name has two common spellings, one with an A and the other with an E, and mine is the latter).
But if forced to identify which is which color-wise, I’d say “grey” has cool undertones while “gray” has warm undertones. Really no reason to think that, but it’s right in my brain.
It’s a setting that’s off by default in Voyager.