I’d agree with Graham. The FS 595B colours that are quoted as a “close match” by some very good colour scheme books are, in my experience and opinion, generally quite a long way from being anything like some of the shades. The original air ministry colour cards are the best reference but are like Rocking Horse Sh*t to find. The RAFM AP reprint is however widely available amongst the second hand book dealers. Ocean grey, and wartime roundel red are mixed for us to a sample but my advice is that the wartime roundel red is a direct match to a couple of coats of red dope (ie not too wishy washy) and this was originally pointed out to me by an ex Spitfire engine fitter I worked with over 32 years ago, when I was regularly model making. I am fortunate to be able to do it on a 1:1 scale these days rather than 1:72!
The wartime red is also a good match to red-oxide paint. Hope this helps you Mike.