Greys but not grays?

Something that's always puzzled me regarding our achromatic spacemen. Why, given the American variants in many words, are they known as 'greys' rather than 'grays'?

I'm under the impression that the main impetus for the greys reaching public awareness were American (Roswell, Streiber, CEIII &c) so why the British spelling?

does it really matter?

Originally posted by monkeybus
does it really matter?

Perhaps not in the greater scheme of things but, given America and its promotion of a cultural dominance over the last few decades, I've always found this as anomalous as the anal-probe wielders themselves.

Could it be intentional, subtly conveying a 'foreign-ness' or a 'difference' to American masses by using 'foreign' spelling? I'm not saying it is, just trying to think of reasons why it should be.