I'm Australian, but does it matter?

I could be describing New Zealand, or Canada, or Belgium, or Finland, or any number of western countries.

It also depends on what spelling corrector you prefer. In Europe you are more likely to choose British English than US English.

I'm not sure how important the difference is for a non-native speaker. For me it definitely isn't, and I mean no offense. It's just, color or colour, both foreign words so its gonna be whatever the default software thought appropriate. But we're digressing :)