There's actually many cases where we (Brits) hate on the American version without realising that actually theirs is the version we were using back when we sent people over to America, and it is us we have changed over the years not they. Still annoys me though :)

When I learned that, I found it extremely humorous. What was even funnier was that the extra U's showed up as Britain attempted to be more French-like. Isn't that a slap in the face today!

I still insist to write "behaviour" despite the protests of my spell-checkers. And I am a Brazilian/Hungarian educated mostly in Portuguese to whom English is a third language.

I blame my high-school English teacher.

But then, when in the browser, I also catch myself submitting forms with control-x control-s.

America is a preservation jar for per-Enlightenment Britain.

Quite. See this supposed American barbarism from Daniel Defoe's 1722 novel "Journal of the Plague Year": "besides, it being in the time of the vacation too, they were generally gone into the country". (http://www.gutenberg.org/files/376/376-h/376-h.htm)

The large majority of -ize/-ise verbs come from Greek words ending in -ιζειν [-izein] (sometimes via Latin, in which they end in -izare). English adopted many of these words via the French, which lacks "Z" as a native letter, and so the -ise spelling.

Americans reverted to the -ize spelling on the principle of spelling words as they sound (a foreign concept to the language, we must all agree), and much of educated Britain likewise used the -ize spelling on etymological grounds. (Thus Oxford spelling [en-GB-oed].) Esteemed English institutions such as the Oxford University Press and Cambridge University Press still use the -ize spelling, as did The Times, until it came to be perceived as an Americanism in the 1980s.

International English, such as that used by the United Nations, follows Oxford spelling and so uses -ize.

Well, it's not "colour", but there are actually a few types in the .NET Base Class Library (BCL) which use the British spelling. Example: the StackBehaviour enumeration (http://msdn.microsoft.com/en-us/library/system.reflection.em...)

I remember hearing a story about how bits of the BCL were written in Britain and originally used "Colour", but they were made to change it to standardise upon american english across the BCL.

The popular ggplot2 library for R uses colour, though I think color is also accepted in some places.

http://had.co.nz/ggplot2/scale_gradient.html

POV-Ray script accepts both spellings.

http://www.povray.org/documentation/view/3.6.0/230/

The British dialects of English have undergone far more change than English elsewhere. Some British dialects were heavily influenced by French, or imitated the francophone "upper" classes so much so that they no longer trill their 'r'. [Citation Needed]

Also, India preserves the vocabulary of the old English bureaucracy, now lost in Britain. [Citation Needed]

Ogre 3D (C++ library for realtime graphics) also uses the word colour, designed by a bright guy from Channel Islands, South England.

BBC BASIC, which does the reputable thing of accepting it both forms equally.