Yes, the vans were another issue indeed - even a few old GSWR six wheeled full brakes survived in traffic until the late 60s.
I see your point about livery descriptions. The "golden brown" as CIE rather curiously described it officially, was of a more "tan" shade than later orangey shades, especially post-1990; these themselves having been the subject of considerable debate on these boards with relation to Mk 3 coaches.
The earlier livery was indeed mostly black, and on many locos in the sixties it was literally all black bar white flashes on the ends - in other words, no tan at all. Equally, a few A's and C's had this with yellow ends.
If "Black'n'tan" is taken as the 1960s livery, this distinguishes it from the "Supertrain" livery of post 1972. From 1987, apart from the addition of the white lines, we have "tippex" or "IR" livery - this is generally taken to mean the 1987- early 90s period, during which the "tippex" white lines were added - the nickname coming from Inchicore painters, and the IR "Set of Points" logo as now applied to 146 at Downpatrick. By the 90s, the "three pin plug" logo appears and we have "IE" livery!
So - 1962-72 "Black'n'tan"
1972-87 "Supertrain"
1987-90s "IR / Tippex"