If you mean a B17 in the ETO, specifically, based in England, then the colour could vary from factory-fresh, rather dark Olive Drab (Green) to almost purple! The most common 'shade' was a brownish-green, the brown being the 'hint' of yellow.
I can't advise on the colours for any of the acrylic ranges, but i normally mix faded shades of OD using Humbrol enamels, No.30 Dark Green, and No.29 Dark Earth. In many cases, it's roughly equal parts, but by adding less of the Dark Earth, you'll get a 'green with a hint of brown'. A touch of thinners, especially with most current enamels, will help with the mixing to prevent premature drying and, if airbrushing, I normally thin about 50/50 or 60/40 thinner/paint. A bit of experimentation should find what you're looking for. If you need it, I can probably find a reasonable colour pic or two showing typical examples.
Note that the B17 paintwork seemed to fade quicker, and more 'deeply, than the B24, and the B26 was notorious for losing paint!