There is a place where the rule for the colon and the rule for the dash overlap, in other words, a place where each one is correct.
...There are several things to consider: money outlay, time spent, manpower involved.
...There are several things to consider -- money outlay, time spent, manpower involved.
In this instance, it is really best to opt for the colon since the dash is so prevalent for interruptions. It is a chance to use the colon correctly and avoid having one more dash in the transcript.
Happy punctuating!
Margie