I call it a K-turn, but yeah, if I say u-turn, I mean I turned 180 degrees in one turn and everyone I’ve ever talked driving with has meant the same.
As a British person who has lived for a long time in America, I have never heard anyone in either country rhyme “color” or “colour” with “poor”, “pore”, or “pour” (and if those three ever differ at all, it is extremely subtle). Those three words distinctly pronounce the R, whereas British and most varieties of American English do not do this for the R of “colour/color”: it is more like CUL-uh. (The R may be there a bit, but normally a lot fainter than in “poor”, “pore”, or “pour”.)
I think i agree with your underlying point, however, that there is no particular difference (beyond general differnces of accent) between how Americans say “color” and Brits say “colour”. (And the same goes for “honour/honor”, “flavour/flavor”, etc.)
A 3-point turn is used in the states, too. It is not a U-turn. It is used when the road is too narrow to make a U-turn. If and when you take a road test for a new or expired license, you will probably have to make that maneuver.
I think we’re mostly there with “thru”. Don’t traffic signs use this spelling? [Does a google search ] Well, here it seems about even, but IME they mostly use “thru”.
Where in the US you at? Americans up North pronounce “color” with a schwa (ə) and a strong “R.” It does not come close to rhyming with “poor” “pore” or “pour.” And only “pore” and “pour” rhyme. “Poor” is pronounced as it’s spelt, “POOR.”
Geez folks, I’m trying to understand what the OP hears differently in “color” and “colour” by using examples of different “O” sounds, not what WE hear differently.
And for the record, I pronounce it “cuh-lore” with the second syllable rhyming with pore and pour, but not poor.
I don’t understand what this means. Pore, pour, and poor are all homophones to this American English speaker.
I offer “The Pourhouse” as my evidence that I’m not alone.
Can you elaborate on how these are different to you?
They’re different to me as well. Pore and pour rhyme with ‘or’; poor rhymes with ‘boor’ and ‘lure’.
That’s odd. I’m a 'murrican, and for me, “Pore” rhymes with “snore”, but “pour” rhymes with “Tony MacLure”.
That’s approximately how I say it, as well. Poor sounds sort of like “foot.”
As for “pore” vs. “pour” some people swear they’re pronounced differently, with the latter coming out as a drawn out “or” sort of like “po-oar.”
OTOH, in some places everything comes out as “po”
That’s why I asked where kunilou lives and is from (where he or she learned English) in the US. I was born in Minnesota and mostly lived in Northeast Illinois. I generally speak with a Northwest Suburban Chicago accent, mostly Generic Flat Midwestern, AKA General American, with a more-sibilant closing S. Not the extreme “da Bearss” sibilance of Chicago itself, though.
Poor is pronounced with an “oo” sound, like “poop” and “droop” (IPA: /pʊɹ/)
Pore and Pour are both pronounced with a long O sound, like “core” and “lore” (IPA: /poɹ/)
I lived long enough in Virginia that “car” and “core” (and “pen” and “pin”) are sometimes homophones, but thanks to a thread in GD I’m a Yankee firebrand tonight. 
This might be important if English was a phonetic language.
Of course if it were, that word would start with an f not ph…
Pore, poor, and pour are all the same, and color don’t rhyme with none of them.
(It does rhyme with per, sir, cur, and fur, however. )
Here’s H.L. Mencken on Webster.
There’s much more on the various changes, when they originated, and their fate in the article.
American spellings would be far more different from British ones if all of Webster’s reforms had taken hold.
Same here, but we’re from the same accent region. I vacillate on the pronunciation of “poor.” Sometimes, it rhymes with “lore.” Sometimes with “lure.” In fact, dictionary.com lists only one pronunciation, and it’s not the one that is homophonous with “pour.”
Any language big enough to encompass multiple dialects and accents is going to have problems being represented in standard written phonetic form.
Standard spelling was a great solution to the idiosyncratic writing of individuals - it meant that if you could read something, you could probably read anything, but as soon as - No - before a standard spelling for any word is defined, it’s already wrong for some people.
Take the spelling of the number 8, for example. To many people, it would seem obvious that this should not be spelt ‘eight’, but should be ‘ate’ or ‘ayt’.
Except that there are English-speaker for whom those two spellings don’t make sense either - in some Scots dialects, it sounds like (how I would write) ‘aycht’ (or maybe ‘eh-cht’). In northeast England, it sounds like (how I would write) ‘eeyit’. Even as I write these renderings, I know they are going to make less sense to anyone outside of my own dialect.
Standard spelling is impossible, but it’s the least worst solution we have come up with so far, for the English language.
Proper capitalization is still looked upon favorably though.
i’ll capitalize if you start using a ‘u’. as a favour of course.
Maybe not the best examples, as poop, droop, and food are typically /Cu:C/ for USers. “Foot” is a good example of /CʊC/.
“Long O”, of course, means nothing, but you might be after /Coəɹ/, /Cɔːɹ/, or /Coʊɹ/, depending on locale.
Dipthongs are really hard without a personal vowel map and a spectrogram of each example. 
But will you, really?