I'm Canadian, so I was taught the English spelling in school (so "colour"). But by living in North America (and with the help of the internet and all), I think I'm more used to read "color" everywhere. The American spelling is also much more common in my field of study (computer sciences).
BUT! Even with all this, I prefer to use the English spelling of "colour" and all is friends (behaviour, odour, flavour, etc. )
I love certain words with the non-American English spelling, like humour, favourite and theatre, but for the most part I think the "u" is useless and I think words should end with "-ize" not "-ise." Though, I think it's all a part of phonetics as well: Alphabetized sounds (and looks) better with American accents while Alphabetised sounds (and looks) better with European/Canadian accents~
"color" just because I use the American spellings.
Not to say that British isn't nifty, though. I kinda like "re" instead of "er" for Theater. The "re" at the end of my name (sumre, pronounced "summer") was because my mom wanted to spell my name differently and thought it'd be nice to take out the M and switch the E and the R.
"Colour" can look kinda nifty, but I prefer "Color" myself. :3
Just saying historical origins dominate a lot. Realized many of the cities are named after british things Ex: we have a town called London, a town was called York until they renamed it Toronto, there's Churchhill ect.