Jawfin, the refurbished sets had the now-familiar red seating in them, and cream walls originally with some decorative vinyls on them. Prior to that, they had what in 1974 was standard British Rail checked blue upholstery and mock-woodgrain effect walls up to luggage rack level, with an off-white ceiling.
Externally, they received the same maroon and blue livery at first repaint, but with a white "diamond" instead of an upturned "v". Later - I'd guess about 1981 - they got the all-grey with maroon band under window level. Those on loan to IE retained that livery much longer, as by the time the last car painted that way (69, I think), came back to NIR, everything was beginning to be "intercity" blue and grey.
Next up was the "suburban" red and cream with orange stripe: I think this was about the time the "Castles" were introduced into traffic - 1986. Some 80 class sets were thus painted, but others got the original (and best looking) blue and grey, with the following: from bottom up, a darker grey band at the bottom of the bodyside, main below-window area light grey, then a yellow / white / black / white band, then blue round windows, light grey line above, and dark grey roof.
The red and cream livery, which did not suit 80 class cars at all, didn't last and railcars painted this way were gradually put into the intercity version. To separate intercity and suburban "fleets" on a tiny system such as NIR was clearly impractical.
Later livery variations (approx 2001 onwards) saw the acquamarine band replace the yellow, black and white below window level, along with the continuation of the blue up to roof level (i.e. no grey band above windows).
Then, latterly, we had the quite ghastly re-incarnation of these sets in "red bull" livery - quite the most stomach churning match of livery and vehicle I've ever seen.
Oh no, that's the sandpit (sorry, sandite) yellow.....