I travelled on these a lot in the late 1980s in Cornwall and the Laira Class 122s, following light refurbishment and asbestos strip at Vic Berry (though they did not do a complete job of removing it apparently) and the seat fabric was a red/blue horizontal stripe. This seat fabric is as per Chris Higgs photo above, though I seem to recall it was a bit more vivid then, possibly it has faded with time. The Class 122s where moved west to replace the Class 142s along with a mixed selection of Class 101 and 108s. The Laira 122s in the late 1980s/early 1990s where, I think 55000, 03, 05, 06, 09 & 12 - all of which are now preserved.
Also 55012, the Dapol model in Regional Railways colours, retained this fabric colour after repainting into Regional Railways colours, rather than the normal Regional Railways grey with blue dots, see the last few frames of: https://youtu.be/BCfmElmu5fs forconfirmation. So it is shame that Dapol have given this blue seats!