I have the following cars; 4 R12s, 4 R26s and 4 R17s. I am looking to create two mixed 6 car trains with varying liveries for around 1969 or just prior to the start of the silver/blue period. I know R17s started off in maroon, and most were repainted red, however I have a picture of a green R17 car (6749) see below, and I know the R26s were delivered in green, and then later I think some were repainted red. The R12s I have I want to be painted in red, although I have seen a picture of two R12/14s in green sandwiched between a pair of R26 cars, see picture, which poses another question; R26s are "married pairs", but in the picture it seems the pair are "divorced". I think I'll keep mine happily married... for now.
Were cars repainted depending on what colour paint was available or was there a regime of painting certain liveries at a particular time? I have seen pictures of trains in the late 60s consisting of cars in maroon, red and green all in the same train (excluding the "black" i.e. dirty cars). I have tried to find details of when certain types of car were painted and in what colour scheme after initial delivery but to no avail.