Nintendo trademarked it as Gameboy Color, not Gameboy Colour! Do you call Fortnite, Fortnight?
Hey it's not my fault Nintendo chose the wrong spelling.
I blame American imperialism :P
In general though, I call things whatever I feel like calling them, for example, Pangolier in Dota2 is called Pangoloid in my world. Bloodseeker is Bloodcyka, etc.
And I've never even thought about how to spell fortnight because I've never talked about that game before. But thanks for the idea. Fortnight it is!
I LOVE ICELAND!