In enamels, it has to be Humbrol. If they're still in business. When I was a kid, I remember an article on painting early war british armor. If my memory serves me right, the blue was matched from an RAF blue, from the long-defunct colour ranges of humbrol authentic colors. My practical suggestion is to go th MAFVA webside and download the relevant pages of british armor color schemes.However help is at hand if you don't want to use enamels! In the current issue of Euromodelismo, which is a crap spanish mag, someone has done a Marmon-Harrington AC painted in the three tone scheme the color refernces are for Tamiya acrylics: X14, Sky Blue (a bit toned down of course) X59 Desert sand, X52 Earth. and XF23 Light blue (for toning-down/highlighting I would imagine). The general effect is pretty good. I've always loved that 3-tone schemefor some bizarre reason..... All the best, Jim.