One of the big unanswered questions, just behind "Is there a God?", "Why do we dream?", "Is our universe the only one?" and "Why did they cancel Firefly but fund Star Trek Discovery?" is "What colour are early war Zeros?"
The only thing I'm certain of is they're not white. Probably. Why we still think they're white is a story for another day, and quite interesting, but I'm not going there now. The debate over the actual colour is still going on - the real experts seem to think a sort of light grey with a green-y tint, and Tamiya and others will sell you some paint for it. The only problem is I don't think it looks "right". I suspect that this is partly because the paints are designed to be used on 1:48 scale models and that at 1:200 for BRS you need to lighten them up. Whatever
Anyway this is how I'm painting mine. It is embarrassingly simple and quick yet I think it looks good enough for the table.
Step 1 undercoat with GW Wraithbone Contrast undercoat spray. Wraithbone is a funny off white colour designed for painting elves or fairies or something, but it just about ticks the box and takes 30 seconds or so to apply.
Step 2 block in the canopy in your colour of choice. I use a light blue but there are many ways to paint canopies and it is personal preference. Also paint the engine cowl. It could be black, but I stopped painting black stuff black on my BRS models and tend to use Vallejo German Grey because I think it looks better. Go back over the bits you missed and the canopy bars with "normal" GW Wraithbone paint.
Step 3 use GW Contrast Apothecary White to paint he panel lines. You follow the panel lines with a thin brush rather than wash the whole area down. This is the longest bit of the process but is still pretty fast.
Once dry, apply your decals of choice and you are done.
The models are A6M2s from the PlanePrinter Patreon printed on my Anycubic Photon, but the process works on any suitable model. Decals are from the "spares" box, mostly Warlord but some others thrown in. Yes it is certainly (probably) the wrong colour, but if these are on the table at a convention 98% of the passers by will see and immediately recognise them as Zeros, which is good enough for me.
Cheers