[parminya]

"Tire" and "curb" were once the normal spellings in the UK; "kerb" is an innovation whereas "tyre" is either an innovation that is coincidentally the same as an archaic spelling, or the restoration/repopularisation of an archaic spelling. The spelling "kerb" upsets me whenever I see it because it's clearly referring to the curvature of the kerb, but fortunately I almost never see it.

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.