I use both Mid Brunswick and Racing Green, both of which I've found quite suitable and very similar. It often seemed to fade lighter on the locos, and its unlikely any got a repaint of green other than Maedbh after 1955, albeit without the snails (described as 'spruced up' but in poor mechanical condition during the period after dieselisation)
It's interesting, it 'seems' like the dark green got purged rapidly from rolling stock from 1955, with very few colour images of them or photos of them with the lighter green coaches, bar the example shown above. This may simply be down to many of those coaches being retired in large numbers as the newer PRs, laminates, Bredin mk2s, came online.