Is the difference between ":" and ".." when pronounced obvious in French? In German, I'd say "Doppelpunkt" and probably "Punkt, Punkt," respectively.
I'd like to add that it is wrong to think about commas, semi-colons, etc. in terms of duration of a pause in the speech. These signs articulate written sentences' syntax, and it sometimes relate to pauses when read aloud, but it is not a bijection. When analysing recordings, J. Drillon (Traité de la ponctuation française) showed that the correlation is really weak.