Life is just too short to get exercised by 'color' vs 'colour' or 'theater' vs 'theatre'.
I would point out that Mr vs Mr. isn't so much a British/American thing as a style preference thing. I was taught two styles of punctuation and layout when typing - 'open' punctuation, which tends to go with a modern, blocked, layout, and 'closed' punctuation, which tends to go with the more traditional indented style.
'open', btw, is where you omit the full stops for abbreviations (ie, Mr, etc and so on).
'closed' is where you include them (i.e. Mr. etc.).
I think you'll find people in both camps in the UK (not sure about the US
).
Yvonne
