Paint colours for an FT17 - I wouldn't worry too much. Use you eyes as a conversion chart because most colour callouts are guesses at best. The Weald Foundation restored an FT17 and did analysis on traces of paint to get close to some original colours, you can see the results of their work here:
https://www.youtube.com/watch?v=Gy_rwgbm66ABarbed wire? All commercial products are rubbish and look unrealistic. Make your own, it's easy. I use a variant of the method the method shown in this video:
https://www.youtube.com/watch?v=oxUNrNdLMzA I use 32 gauge beading wire (which is more in scale for 1/35 than the picture wire the guy uses in the video) and also I use a simple jig to make it. I get a piece of 1"x2" wood about 36" long and hammer a nail in at each end. I take a long length of beading wire (more than twice the distance between the two nails), secure it at the halfway point to one of the nails and then twist it together to form the central core of the barbed wire. Once the entire length is twisted together, I secure the loose end to the other nail and then do the "s" shaped winding of the third piece of wire along the length of the core. Having the core wire held in a jig makes it much easier to do the "s" shaped windings to make the barbs compared to the video. I tend to secure each of the barbs with superglue before I cut the excess "s" shaped windings off.
You can then paint and weather to your taste. The results look far better than any commercial product (which tend to be flat 2D etch). Here's an example.
