Reply To: I can see how Nick mighta not got it…
It should be possible, because the operating system doesn’t see colons and semicolons, it sees a lower-level representation of the keys. For example on Linux they’re called keycodes or scancodes. There’s a table that translates these into the key symbols. You just need to change it so the normal press generates a colon and the shifted press generates a semicolon.
xmodmap -e "keycode 47 = colon semicolon"
The above command would accomplish what the caller was asking. I’ve no idea how to do it in Windows but there should be a way.