According to the WS Datafile, Jamo is correct, some of the earlier machines had standard day lozenge, oversprayed for night work, so Aviattic lozenge would work. The engine nacelles were "frequently left unpainted, or perhaps coloured light-grey", struts were "painted dark blue or green". Those areas that appear to be plain coloured, such as forward fuselage and sometimes the nacelles, were probably dark blue or green.
In other words, do what you think looks right!
Ian