CDRJC: light green on paintwork timber, eg window frames; walks Indian red and deep cream.
MGWR: red and cream
GSR: dark green and dark cream, often separated by a black line about an inch thick
CIE: until the 1960s, generally much the same as GSR, but as mentioned from the very early 60s red and cream schemes appeared here and there, including West Cork. Amiens Street got light blue at one stage, and various one-offs were to be seen around Dublin. After that, two-tone grey and white was universal, as also mentioned above. IE days brought a dark green with a bluish tint, also the two tone blue and red referred to; latterly the grey and cream (which I must say I personally think us awful, but that's only my opinion!)...
GNR: very similar to GSR internally (green and cream), but externally shades of browns and red on occasion; also green like GSR. The GNR painted station signs variously in red on a white background, black on a yellow background (this being continued by the UTA and spread to ex-NCC and Bangor line), and white on a black background.
White lettering on black backgrounds seems to have been standard on a lot of railways. The GNR had it in early says, and the GSR used it mostly, though Fenit at least was black on white.
The MGWR had navy blue signs with white lettering, as did the WLWR.
The BCDR had stations painted as now accurately reproduced on the DCDR. Fencing was often silver looking as it was painted (even if wooden) with the same sort of galvanised silvery grey paint as used on bridges!