Reason: I've swapped my semi-colon and colon commands so that entering the command-line takes one less key-stroke:
nnoremap ; :
nnoremap : ;
vnoremap ; :
vnoremap : ;
nnoremap q; q:
But in the command-line prompt, the colon character still shows up. I would like this character to be a semi-colon instead so my brain doesn't have to deal with cognitive dissonance.