Hi Roachie. No idea about the decals but with regards to Humbrol I've tried a few which I've included below to compare.
I admit I'm at a loss to remember what brown was applied to what and when. I'll do a bit of research to try and get something right then can't find the correct paint, or I get the research wrong. But now I'm unable to get paints like Raileys mailed and never tried Floquil before they disappeared, I have to rely on Humbrol alternatives from the LHS. I think I read in an AMRM review that the Raileys IR and Tuscan were accurate so the top two carriages represent their Tuscan and Indian Red respectively. As a kid in the 70s, all I remember was everything was a grimy red/brown and I figure near enough with some weathering will do for me in model form, but that's me. I can sympathise with anyone seeking more accuracy.
So here's an attempt to compare a couple of Humbrol examples of what I've done matched with what's marketed as Indian Red and Tuscan for engines plus Raileys for comparison.
From left to right and working down;
-The Bergs N was brushed with Railey's Tuscan, the bottle lying next to it. To me I thought it was too light, but I don't know.
-The RUB carriage next to it was sprayed with Raileys Indian Red. No bottle to show.
-The RUB PHS was done with Humbrol Matt 70. Paint tin to the left of it.
-I've recently done a rake of six FO carriages and they were painted with Humbrol Satin 133, the paint tin to the carriage's right.
Both the PHS and FO have been weathered slightly but towards their rooves the paint is untouched. There is another tin further to the right which is Humbrol 113. A Matt finish, I bought it ages ago as an alternative and did paint something with it but not sure what. It seems lighter by a smidgeon compared to the other two with a hint of more purple perhaps??
-The three engines below are factory colours; an Auscision 45 factory Indian Red, TOR 49 Indian Red and below that, TOR 4450 as Tuscan. They very much look the same to me. Despite light catching the curves in the photo, looking at them in person I still can't tell the difference.
The second photo shows an Auscision 422 in Reverse scheme compared to the other three engines. I can't remember what I've read about what brown was used in the Reverse scheme but in this one it's much darker. I've only got early Austrains 80 reverse to compare and all my 80cl look the same brown.
Looking back I think I've shown what not to use for Tuscan

To me I really liked 70 and 133 as generic NSW browns, but not Tuscan if Tuscan is that Raileys hue. Anyhow, looking at the Humbrol site and comparing the Raileys Tuscan, I think Red Brown Matt 100 might be worth a try.
http://www.humbrol.com/us-en/catalog/product/view/id/970/category/110/ Next days off I'll try and get some and give it a try.
https://flic.kr/p/qVjgnShttps://flic.kr/p/rzNiMo