Regex match all occurrences of a character except the first without using \K

I have this pattern which works fine but since I'm using Java I can't use the \K operator.

(?:\A[^:]*\:)?+[^:]*\K\:

How can I change this so it works the same but without \K ? It should match every colon in a sentence except the very first one for each new person.

Jason : Ok thanks for everything : here we go, no need to : etc.
Martin : I don't think it's much of a problem but we definitely need to fix this error before we run : out of time.
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