For grammar sticklers here's the deal on gray/grey:
Gray is used mainly in US and other areas that use US English. Grey is used in Great Britain and areas that use UK English (like Canada, where I'm from). Exception is proper nouns such as a last name (which is how my grey-mix kitty, named after Brit character Dorian Gray gets spelling for his name). Too confusing IMHO
But anyway you spell it, your kits were adorable kittens and are stunning grown-up kits!