True, colons are used for lists. However, they have other functions and, of those, a most important one: to draw attention to a point being made.

In the sentence we're been examining, the colon isolates the specific point of reference, draws our attention to information the reader can focus on. A dash, instead, would indicate that a clause is about to trot down that final lane. But there's no clause that follows that dash in what Milo suggested. I'll continue to happily disagree with the proposed dash for this particular sentence.

Edit: Here's a url for a good overview of colon use:

http://www.mccc.edu/students/tutoring/colon.html