The /ʌ/ vowel is spelled with <u>, <o> in colour and come, and with <oo> in blood. The /əʊ/ vowel is spelled <oCe>, <ow> or <oa>, and appears in the letter name O. Notice the homograph does.
This is a contrast between a short vowel and a diphthong with a similar starting position but distinguished by lip-rounding. It does not seem to be a problem for many learners.
There is a taboo word pair in fuck/folk.
Interesting pairs include:
muddle modal
mutter motor
suffer sofa
The density figure is 3.2%. The set makes 104 semantic contrasts giving a loading of 50.7%.
blood blowed bud bode budded boded budding boding buds bodes buggy bogey buggies bogeys bun bone buns bones bunny bony bused boast bust boast busted boasted busting boasting busts boasts buster boaster busters boasters but boat butt boat butted boated butting boating butts boats butter boater butters boaters buzz beaux buzz bows chuck choke chucked choked chucking choking chucks chokes chukker choker chukkers chokers cluck cloak clucked cloaked clucking cloaking clucks cloaks colours colas come comb comes combs coming combing comer coma comers comas coming coaming comings coamings Corunna corona crumb chrome crux croaks cud code cull coal culled coaled culling coaling culls coals cult colt cults colts cunning coning cup cope cupped coped cupping coping cups copes cut coat cuts coats cutting coating cuttings coatings does does dost dosed drug drogue drugs drogues dull dole dulled doled dulling doling dulls doles dumb dome flood flowed fuck folk fucks folks fuggy fogey fun phone fund phoned funny phoney fuzz foes glut gloat gluts gloats glutted gloated glutting gloating gull goal gulls goals gulled gold gully goalie gullies goalies gush gauche gust ghost gusts ghosts gut goat guts goats hull hole hulled holed hulling holing hulls holes hull whole hulls wholes hulled hold hum home humming homing hums homes Hun hone Huns hones loves loaves luff loaf luffed loafed luffing loafing luffs loafs lumme loamy muck moke mucks mokes mud mode muds modes muddle modal muddles modals mull mole mulls moles mullah molar mullahs molars mulled mould mussed most mutt moat mutts moats mutter motor muttered motored muttering motoring mutters motors muzzy mosey none known null knoll numb gnome numbs gnomes nun known nut note nuts notes nutted noted nutting noting puck poke pucks pokes pucker poker puckers pokers pun pone puns pones pup Pope pups Popes rub robe rubbed robed rubbing robing rubs robes rug rogue rugs rogues rum roam rums roams run roan runs roans rust roast rusted roasted rusting roasting rusts roasts rut rote sculled scold smut smote son sown spud Spode struck stroke stuck stoke stud stowed stun stone stunned stoned stunning stoning stuns stones succour soaker succours soakers suck soak sucked soaked sucking soaking sucks soaks sucker soaker suckers soakers suffer sofa suffers sofas sully solely sup soap supped soaped supping soaping sups soaps ton tone tons tones tubby Toby tuck toque tucks toques tun tone tuns tones tunnel tonal tunny Tony tup tope tups topes tut tote tutted toted tutting toting undercut undercoat us O's
Credit: John Higgins