Coach colours - Great Western Region 1955-65

Chocolate and cream was re-introduced on the Western Region from 1956. Initially it would have been used just for the most prestigious named trains, but latterly I think chocolate and cream coaches got mixed in with the others. Only BR Mk 1's would have received this livery.
The other two-tone livery would be carmine and cream a.k.a. "Blood and Custard" which was the earliest BR livery and was superseded by plain maroon from about 1956. But examples could still be seen until the early 60's.
In B&W photos, chocolate & cream livery can be distinguished from carmine and cream because the former would bear the BR lion-with-wheel-in-its-paws roundel, while the latter carried no insignia.
Branch line and suburban stock would initially have been plain carmine, and later maroon.
I don't think blue and grey would have been seen on the WR until after 1965.
I expect that's a bit of a simplification, but I hope it's useful.
Andy Kirkham Glasgow

Before about 1860 Crimson and cream, with possibly BR Maroon (on main line stock).
After about 1960 BR Maroon, probably Chocolate and cream, with possibly Crimson and cream (on secondary line stock).
BR Blue and Grey was only just being introduced in '65 after it's use with the XP64 experimental / exhibition train of 1964.

"Luke Briner" wrote
During the BR era only a limited number of *top-link* coaches (mostly those used on *named trains*) were painted into chocolate and cream from c. 1956 onwards from memory. The chances are therefore that you are looking at crimson & cream, or standard maroon (from c. 1956) for the ones painted in a single livery. Some suburban stock prior to 1957 could have been in unlined crimson.
The first general application of blue & grey was from 1965.
John.

BR blue and grey began being applied from 1965 onwards, after the re-branding of 'British Railways' into 'British Rail'. Chocolate and cream carriages were initially only permitted by the British Rail Board to run on named trains (from 1956 onwards), thus the Western Region invented as many named trains as possible to return to its beloved colour. In 1955, the stock would have been blood and custard / crimson and cream, which was applied to all regions from 1948 onwards, but this proved to weather badly, thus maroon was pioneered on virtually all regions from 1956, except the Southern, where the familiar green livery was permitted. However, I believe that there is a variation in shade between the maroons of the Midland, Eastern and Western Regions.
By the time blue and grey Mk 1s began arriving in force, Western Region steam was in its death throes, with diesel hydraulics having taken over most of the work. The last steam-hauled train out of Paddington was on 11th June 1965, whilst the last Western Region steam locomotives were withdrawn from Tyseley in November 1966. A good mixture of blue and grey stock with regional colours could usually be seen on the Southern Region main line to Bournemouth, where whole coach rakes of the British Rail 'modern image' were fronted by a steam locomotive, right up until July 1967.
This is how I understand proceedings, although I am sure I will be corrected for any erroneous points.

Not intentionally! Many Mk1s were delivered new in Maroon and coaches for all regions came off the same production lines. But there were variations between individual coaches depending on how long since there last repaint and how well they weathered. Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.

Having watched a fair number of colour videos of early hydraulics, there did seem to be quite a few trains around in 1960/61 approx where the coaches were in all 3 liveries of carmine/cream, chocolate/cream and maroon in the same train, so I think you are safe to have formations with various combinations of those liveries. O/T slightly, but I have also seen rakes with a mix of carmine/cream, maroon and green on Exeter - Waterloo services. However, I have never seen a photo or film of the four different liveries in one train. If anyone out there knows of one, I would love to see it.