Personally, I've always liked the English way. It seems so much more cultured :P
Though, generally, I just write 'color' when writing a paper or the like. I just have to remember to write with 'u's if I'm writing in an English setting... I'm working on a short story set in England now, actually, for World History class. I'll have to remember that.
3) There is not much to this thread and may be locked as "versus", "favorite", or the like.
I think it well explores the depths of the specialties of dialects and accents and the like. I hardly find it a 'preferred' or 'which is better' - it's how you're brought up, or your sense of flexibility when it comes to the issue.
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"favourite"*