I'm ok with the double colon idea for exit ramps, but I do think it looks odd like others have noted. Even though it is two more characters, I personally prefer "Exit 220: I-310 S to Boutte / Houma". Due to screen space available, it's not optimal, of course, but it's more accurate. For really long signs with multiple routes and control cities, a colon or "to" isn't going to make a difference on what fits on the screen because most of it doesn't anyway.
On-ramp naming has long been a peeve of mine. I think we can have it such that if there is a control city or destination, we can eliminate the word "to" and use the convention similar to off-ramps. But if there is only a ramp going to a route, then having the word "to" remains important to keep the ramp name different from the route.
