Bold colours are needed for a strong corporate livery. Think Cadburys, Coca-Cola, Yellow Pages etc. that's why the black'n'tan worked well for forty years.
The drab greys of the "Enterprise" were woeful from the start. I always thought some sort if bright red and white, like Virgin Atlantic, would have worked well for that. To have a separate DART livery, to me, demands the same on the trains and buses - call it the "jackeen" livery (two tone blue would be no worse than many a thing).
Everything else in a clearly identifiable IE livery. If green, so be it; but a bright green, not a wishy washy one - and grey is all right for a freight loco, but not paired with green as a strong passenger livery. Stations should be the same colour, like in "CIE green" days.