I was reading over earlier posts on this thread with regard to the original idea of a 1910-ish GSWR layout, which, as I agree with others is a superb idea especially with scale track. While track has to come before locos, coaches, wagons or stations, a few pointers re GSWR liveries might be of interest, since you referred to the "battleship grey"'s drabness as a reason not to model GSR or CIE.
The green used on 36 in Cork is not quite the right shade, though the lining is probably as close as one will get now. For such an important company, it's odd that (to date) no definitive information seems to exist in relation to loco green (or carriage colour) in the days when 36 was in traffic. But that's just an aside, since you asked about 36's colour - it's certainly jot CIE green either, by the way.
The GSWR green livery started to disappear about 1895, being replaced by black lined with red. Numberplates had red backgrounds (immediately "greyed over") after about 1915! Therefore, for 1910, the liveries in daily use were actually - overall - a good bit darker and gloomier than the later grey, but probably more pleasing to the eye.
Locomotives: the odd one, old, possibly still in the dark olivey green, as seen (accurately) on No. 90 in Downpatrick which has exact paint match. However, in the later years of the green, 1885-95, the lining was cream and black, not the style on 90 which is accurate for 1870-85. The vast majority of locomotives, therefore, would be glossy black with red lining.
Carriages were painted the colour worn at present by the RPSI's 1142 and 351, or the DCDR's 836. This a very dark browny maroon known as "lake"; mind you, I'd be scared of finding something radioactive in a lake that colour!!!! Some mainline stock had the cream upper panels as seen on 351, but the bulk of carriage stock was six wheeled, and neither they nor the majority of secondary bogie stock did - these were all-purple-lake, like (accurately) 836.
Wagons were - wait for it - mostly black!
I have details somewhere of what way stations were painted. I'll pits it when I can find it.
If you like the green on locos, you're looking at the 1870-1900 period....