Actually, I disagree there. Words like Armour (Arm - err/urr) and Colour (Col - err/urr) are spelled like they sound. Armor (Arm - or)and Color (Col - or) aren't. Imo anyway. Maybe it's an accent thing.
It must be related to accent Xordan because I know for a fact that the way people pronounce color where I am would have to be spelled "color" or the sound of the word wouldn't match its spelling. The same thing also goes for armor.
I have to wonder though do you pronounce part of "colour" with the same sound as "our" as in "our shoes".
*edit*
This was taken from
http://en.wikipedia.org/wiki/American_and_British_English_spelling_differences.
Most words ending in unstressed -our in Britain (e.g. colour, flavour, honour) end in -or in the U.S. (e.g. color, flavor, honor). Most words of this category derive from Latin non-agent nouns having nominative -or; the first such borrowings into English were from early Old French and the ending was -or or -ur. After the Norman Conquest, the termination became -our in Anglo-French in an attempt to represent the Old French pronunciation of words ending in -or. The -our ending was not only retained in English borrowings from Anglo-French, but also applied to earlier French borrowings. After the Renaissance, some such borrowings from Latin were taken up with their original -or termination; many words once ending in -our (for example, chancellour and governour) now end in -or everywhere. Many words of the -our/-or group do not have a Latin counterpart; for example, armo(u)r, behavio(u)r, harbo(u)r, neighbo(u)r; also arbo(u)r in sense "bower"; senses "tree" and "tool" are always arbor, a false cognate of the other word. Some 16th and early 17th century British scholars indeed insisted that -or be used for words of Latin origin and -our for French loans; but in many cases the etymology was not completely clear, and therefore some scholars advocated -or only and others -our only.
From this it sounds like English was forever changed after the Norman Conquest. It also sounds like when a word has an "our" ending in Britain and an "or" ending in America most of the time that word was derived from a Latin word that ended with "or".
If this is true then in most cases of words with "our"/"or" differences the American form is actually more philologically correct.