I often see lists written as follows (using em dashes to elaborate a list item):
- Item 1—explanation for item 1
- Item 2—explanation for item 2
Is this generally correct, or are colons preferable?
While I'm not a typography specialist, I propose this to think about:
A colon might be useful for mappings between items and some associated, but generally unrelated information:
(inspired by the 30-day song challenge on Facebook)
If you write something which really elaborates on the item itself, you might use an em dash instead of a colon:
Another way to put it: Dashes are OK in situations where parentheses would also be acceptable, as in my second example, and probably also in your original example. Colons are to be used if the real information is after the item, as in the song challenge example. Parentheses would not be acceptable there, so I would prefer colons over dashes.
These are just suggestions; other people may prefer it the other way around or simply use them interchangably.
Also note that there are various definition environments in LaTeX and a definition list (