Only seeing this now.
I have no information on woodwork colours of the WLWR. being a very short lived concern, it's possible that it was a continuation of that of the W & L; I am unsure, however, of what way they painted stations.
The MGWR painted buildings, station furniture etc., with cherry red and cream or a stone colour. Station signs were either white letters on black, or navy blue enamel signs with white lettering; this, however, would fade to a creamy colour after a while.
The GSR painted stations a darkish leaf green colour, not unlike earlier CIE green; and cream. The green and cream tended to be separated on upright poles, for example, by a half-inch black line. This was continued well into CIE days, right up to the early 1960s.
In 1900, carriage liveries were as follows:
WLWR: Same as their locos, lined maroon. Carriage lining was, i believe, gold; possibly gold and black. The maroon was quite a dark shade.
MGWR: In 1900, plain mid-brown with gold lining. The blue / white livery, and the brown lined in yellow, and their variety of deep maroon, would come later.
GSR: If we're in the 1930s, a few carriages are still rattling about in CBSCR, GSWR, MGWR and DSER liveries; most within their own territories. Actual GSR livery can be summed up (and I'm focussing on, say, 1935) as follows:
1. Standard carriage livery: Deep maroon / brown, known as "crimson lake", despite being no more crimson than yellow tartan! This is now accurately shown on the ex-State saloon, No. 351, now in the care of the RPSI, and the GSWR third, No. 836, at Downpatrick (though it should be noted that the white upper panels there are not accurate for that particular type of vehicle). This would be lined in gold, with full crest, initials and carriage numbers as shown in numerous photos. This was applied to all stock except for the following. This gloomy shade was in fact the same that the GSWR had used, and probably not much darker than the maroon livery which the MGWR had had from 1918-25.
2. "Main Line" livery. This was brown and cream, both shades the same (or close enough) to the livery of the Great Western Railway in Britain. The colours were separated by a thin black line, I'd say half an inch thick. The brown came to waist height, and cream from there to the (dark grey or black) roof. Above window level were two more thin black lines - one directly above the window line, and the other just below roof level. This livery was said to be intended initially for main line corridor stock only, but I have seen a single photo (and a poor one at that) which appears to show a six-wheeled passenger brake van clad thus. It's safe to assume this was an exception of some sort, as forty years of my perusal of old photos, particularly in the collections within the IRRS when they were available to members, failed to produce a single example of anything but main line stock in brown and cream. Narrow gauge, branch line stock, all 6-wheeled passenger stock, and older bogies were all concurrently in the "crimson lake". This brown and cream livery seems to have lasted from about 1929 to 1934 or so, but with infrequent repaints of some stock, carriages in that livery were probably still to be occasionally seen at the outset of the CIE era.
3. "Steels" livery. When Edgar Bredin planned the first steel-panelled stock, which though now known as "Bredins" (despite jhb171's grandfather's scrawl being on the drawings!), were then known as "the steels", they would enter traffic in a new livery. Perhaps they were tired of copying the GWR of England, so now they produced a livery virtually identical to that of the English LMS! A lighter maroon - LMS "red" (actually a light maroon) was chosen, lined in an identical manner to the NCC, and the LMS. This had a yellow / black / yellow line below window level, with twin yellow lines above windows - again, like the brown and cream, there was one line above the windows, and another below the gutter line. All stock of all types and both gauges would gradually be repainted this way.
Thus, in 1935, it depends on what type of carriage you have. If it is older coaches, the deep purply brown. This would include non-corridor stock and all 6-wheelers. More modern wooden coaches (usually the high-roofed 1915-1925 designs) will be perhaps two thirds brown and cream, one third older purple lake. So, six models - 4 in brown and cream, 2 in lake, perhaps. Any newer Bredin type, whether suburban or main line, LMS style lined maroon.
In terms of being lost in the mists of time, eye witnesses may be, but accurate information survives. Livery accuracy is almost entorely ignored by preservationists, artists, even some modellers, maybe it's just not our thing in Ireland. But in Britain, they go to extraordinary lengths to get it right. Thus, and properly restored LMS coach over there - and I'm sure Precision Paints have proper LMS maroon. Equally, they'll have GWR brown and cream. The accurate GSWR colour may be seen onthe two vehicles mentioned above, but also on the large scale model dining car made by GSWR apprentices, and now on display in Cultra (surrounded by full size things inaccurately decorated!).
I hope that this is of assistance.