Great looking models, always nice to see another Caley modeler!
I've done a few similar conversions using the old tri-ang coaches. My initial plan was to create a 4 coach set of brake third/third/first/brake third as commonly seen in period photos. The problem with trying to use the tri-ang coaches as brake thirds or compos is that the Caley used lookout ducts and end windows (not the best of descriptions!) which would make a challenging conversion, even the Decent Models brass kit is a tad difficult to get right!
I used Phoenix paints Caledonian Purple Brown (dull) for coaches and those in one of my old threads you previously linked to. Horse boxes (along with other non passenger stock) seen to have been painted in one of two different liveries depending upon the style of the body paneling. NPCS with passenger carriage style paneling were painted in the purple brown/lake/madder of the coaches while NPCS with planked bodies or which were based on goods stock were painted in a dull brown or 'chocolate brown' livery with yellow lettering.
A cut and shut of two tri-ang brake thirds running on a brassmasters 6 wheel underframe. I painted the ends vermilion as a best guess based on the info I could find.
Another cut and shut. Runs in a fixed set with various other 4 wheelers from a variety of sources.
This one is just a repaint representing a former full first down graded to a composite. Just needs lettering and different coloured seats to represent a compo, no body modification was carried out. Sorry the quality, the battery died rather unexpectedly!
My attempt at a scratch build horse box part way through an upgrade. I used Tamiya Flat Brown to represent the 'chocolate brown' NPCS livery.
Good luck with your conversions!
Ross