I took the liberty of asking over on English L&U about the differences in a range of words that could appear as tags of this kind:
Responses vary between "they are the same", "colloquial refers to speech/conversation", "colloquial means provincial/regional"
So for our tagging purposes is it most useful to think of colloquial covering the same scope as informal? And if not, what kind of wording should we use in the tag wiki of each to clarify the difference?
Are the two tags currently used in such a way that would indicate a preference for one particular sense of "colloquial"?