I sure it doesn't really matter, but I noticed the other day that that package name for the Ubuntu Software Centre is
software-center which is the American spelling of center, so I thought it would probably be preferable for me to use that spelling in general when discussing the Software Centre even if not using the package name?
I guess most of the others don't matter
Colour - Color
Behaviour - Behavior etc etc etc.......
Of course if doesn't mean I'm ever prepared to use the expression 'do the math' shudders ;)
And in the unlikely event there is a question involving association football then I will have to call it football and not soccer as it's a well known fact that:
Whenever an American calls football soccer, an Englishman dies.