Ironically, colour (like a few other ou-isms) is actually a modern French influence that took root in Britain but not "in the colonies".
As a Brit, I think it's a tad unfair on the yanks to see them as that parochial. As a test, ask any Brit moaning about the NHS and railing against the US private system (these complaints often come together from people who would never consider themselves parochial) whether the health services of Germany, France or the Netherlands are private. They won't have the first clue.
Just shows you, all that consumption of worldly and international news by worldly and international types remains strangely parochial, and that's just one example.
Now, they're thought of as American.
Also, more vague but fascinating, is that the American "southern accent" (quotes because there isn't a single southern accent, but most people think of a specific one when they think "southern accent") is largely a "British accent" (quotes for the same reason), but British circa the 1700s.
This is actually a fascinating subject, well worth looking into if you're interested in English language history. Also interesting is that the division between American and British English has been growing softer over time, and more and more modern Britishisms are being used regularly by Americans (and vice versa).
The various accents do tend to have features in common, though, so you can hear that the various southern accents are part of the same family, and similarly with the various British accents. There are, of course, exceptions to this as well. This bit of linguistic history is really referring to a fairly specific American accent and a fairly specific British accent.
The Southern accent in the US did not emerge until after the Civil War, replacing a diverse array of local accents. It came from the Appalachian South which was settled by the Scotch-Irish and Germans, none of whom had English accents.
I do hear "gotten" said occasionally in my part of the US, but it's not common. It's a bit like "ain't" in that way.
Likewise, spellings like "programme" are deliberate changes to mimic the French spelling. These have been rather more successful than they have any right to be, but some have completely failed (like "gramme") and a lot of people still use the older spelling.
-ize, also, used to be the standard spelling with -ise an alternative also found in the UK. In this case, it's clear that an understanding that -ize is used in the US and -ise is used in the UK became an understanding that -ize is the US spelling and -ise is the UK spelling which raised its currency. But I think they both remain in use in the UK (-ise has more-or-less chased out -ize in Australia though).
-or spellings like "honor" and "color" were once much more common in places where they are now rarely seen and vice versa. To an extent they follow the same story as -ize/-ise, with the US standardisation of one chasing its use out in the UK. In Australia, -or was much more common (than now) when the power to distinguish oneself from was the UK, but now that the main power one needs to distinguish oneself from is the US, -our has chased it out except in the name of the Labor party (because the paperwork was filed by someone who happened to prefer the shorter spelling in a time when both were current) and some uses of "honor" that are literally etched in stone. (The last general use was until about the year 2000, by "The Age", a Melbourne newspaper which used -or as its house style, but by then it was seen to be improperly American and they switched to -our.)
Generally, spellings and spelling variations remain open and subject to gradual change in all English-writing countries.