I think the can of worms was open before I started building!!
Looking through the Oakwood press book about the railway, the livery is based on the "Lake" and "White" livery. As you mentioned above, basically mirroring the LNWR scheme. Although the image above doesn't show it, it is a deep blue/plum colour below and creamy/white above.
I'm sure you realize how hard it is to build a colour scheme when all you have is black and white photos. I think when the southern railway took over, the stock was painted all one colour, whether this was green to match the standard gauge stuff, i don't know!
Anyway, now the coaches are built, it won't take too long to change the colour of the stock. I have a dark maroon version sitting on my pc, as I was sure they were originally that colour!
Anyway, i'm open to healthy discussion and change! I plan a southern version set eventually as well.
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As for the track texture, Michael has let me distribute my modified version, so I will upload it sometime soon.
Cheers, Chris