From what I've seen of various aircraft from WW2 to present day, the blue lens, when used with a 'warm' bulb, gave a bluish green light, although 'modern day' lamps do appear blue, more so with high-intensity or strobe light sources.
Some WW2 types did indeed have a lens which, when not illuminated, appeared to be a bluish green, or greenish blue, rather than true green, and this might be something to do with the visibility of this colour, compared to straight green, as well as the supply source, aircraft type, factory etc etc.
Looking at some of my pics of restored WW 2 types, most seem to have a blue lens, quite dark in appearance when there's no light passing through the material, either from the lamp itself, or external sources.
I also noted, in a brief scan through my photos, that at least one restored Hurricane appeared to have clear lenses, using a coloured bulb, whereas wartime photos seem to show both clear and tinted lenses, in B&W photos. Again, this was presumably due to the production factory or supply source.