See the results of this poll: Pronouncing Colin.
Respondents: 50 (This poll is closed)
- Call-in : 35 (70%)
- Co-lin (co rhymes with go) : 3 (6%)
- Other: 12 (24%)
Neither. I say it COL-in. Sounds very different to ‘call’ imo, but that’ll be because of the difference in the way English and Americans pronounce the letter O.
I don’t know what you meant by the first option–did you mean like the word call or like in [name_m]Calvin[/name_m]?–but I pronounce it like [name_m]Coll[/name_m] in (rhymes slightly with collar). 
I generally say CALL-in, but if I met someone who pronounced it COH-lin (rhyming the first syllable with “go”) I’d say it the way they did. I’ve met/heard of people saying it both ways so I think both are legitimate and you could use either.
CO-lin, CO with a short o like in cot, got, not
The only person that pronounces [name_m]Colin[/name_m] like the body part “colon” is [name_m]Colin[/name_m] [name_m]Powell[/name_m]. The long “o” pronunciation is not the “norm” for anyone else and I find it very odd. I pronounce like [name_m]Colin[/name_m] [name_f]Firth[/name_f] (short o).
Col like the first syllable in collar.
Ditto, CopyandPaste.
Col (like “hot” “got” “not”) - in.
I’m American but I agree with this. I’ve never heard [name_m]Colin[/name_m] sound anything like “call in”. Col- has a short “o” like cot, got, and not.
COL-in. I’ve never heard it pronounced any differently
I say coll-in
Another for coll-in.