Collocations for collar - noun

open, undone (esp. BrE)
His tie was knotted below his open collar.
His collar was undone.

button-down
spread (esp. AmE)
high, stand-up, wing (esp. BrE)
tight
starched, stiff
detachable
coat, shirt, etc.
fur, lace
clerical, dog
The minister had his dog collar on.

have
The shirt had a button-down collar.

have on, wear
button, do up (esp. BrE)
adjust, fix (esp. AmE), straighten
He was standing in front of the mirror, adjusting the collar of his shirt.

unbutton, undo
pull up, turn up
She turned up her coat collar for extra warmth.

pull down, turn down
loosen

button, stud
size

collar and tie (BrE)
He wore a collar and tie for the occasion.

dog
flea
choke (AmE), radio, training (AmE)

have on, wear
slip (BrE)
The dog slipped its collar and ran off.