I like the colour coded displays from an "ooh it looks nice" standpoint, but I imagine it will end up much like the experience in the P13/14 lounge at Piccadilly (insult to injury to come from a place served by trains on that platform), I can't really say it helps to calm my anxiety about getting on the platform and actually getting on the train.
If one were to suggest ways to improve the existing board rather than have these things in the middle, I propose that you could change the called-at stations to one scrolling line, then make the destination and TOC names bigger and finally put a massive platform number up in the middle. I don't know about other people but generally I already know that, for example, if its going to Glasgow or Edinburgh or Blackpool then it will call at Lancaster or Preston, so that's my train. Of course this won't help you if you have no idea which of those routes has your stop on it, but then again these are big long distance trains that you don't exactly walk up to and get a ticket on a whim, so you could just find some way of making it clear on ticket purchase which train you're getting on.
Euston’s ceiling and floor are its two redeeming features - why not take out both at once?!
Euston's ceiling is certainly not a redeeming feature, I think its one of the reasons I hate the station, the platforms are extremely gloomy and generally the entire place makes me want to run out the door as soon as possible so I can get some light and some air (and have a smoke.)
I think the other bit about it is that there's so much distance to cover getting anywhere in the station. Getting from the platform from the concourse to the exit, going to the loo. While I don't tend to travel up or down when its at its very busiest I can't help think that it would be a great improvement if you could move from platform to platform easily without going up to concourse level. Then you could shorten the length from front to back of the concourse and get people onto the back of the platform level. Also why is there never anywhere to sit? Lime Street has benches, Piccadilly has that screen and bench flower thingy, but I can't seem to remember seeing any seats at Euston.
To top it off, I hate the plaza as well, it is a pain in the arse to get up and down from street level especially with luggage and makes the surrounding area more difficult and hostile to navigate. Sorry if this rant is out of place but man it would be great if the west coast had a nicer London station.