I was just asked a question about the number of spaces to use after a colon. It used to be standard to use two spaces after both a period and a colon. Now one space after a period is acceptable, even preferred. (I still have trouble making my thumb obey and hit the space bar only once.)
I have never read anything about spacing after a colon, though, so I tried it: what do you think about one space? Or look at this: here are two spaces.
One space looks fine to me. What do you think?