I painted the (hopefully) attached roundel on my CMP roof using the following colours:
BS381C 356 Golden Yellow
BS381C 110 Roundel Blue
BS381C 538 Cherry Red
There is no white in the BS381C range so I used a white signwriter’s enamel.
I bought the paint from Paragon Paints and it’s semi-gloss, not matte, as that was too flat against the matte SCC2 I had mixed at Williamson’s in Ripon from Mike Starmer’s swatches.
I cannot remember where I got the colour information from, but I looked at several modelling forums at the time as those guys like detail. It is round in real life as well, the angle of the shot makes it look slightly oval!