It is indeed a fascinating subject, and one that really needs a lot of careful research when drawing conclusions. The schemes themselves are complicated enough before you start to consider the vagaries of photography, how the photographic chemicals then represented the colours (orthochromatic film vs panchromatic), how poor some of the photos were being just snapshots.
Then you get the human frailties, like recollection of colour. Describing colour in the first place is hard enough without working in the fact that people are very poor at recalling colours.
And then we have the surviving relics, most of which are not their original colours due to ageing and the efforts to preserve them over the years. You can't really be sure with complete aeroplanes because we don't have records of what has happened to them in the intervening 100 years. Finally, there are the number of relics that are actually fakes. Pieces of WW1 aeroplanes were desirable at the time, hence the trophy hunting that went on. Add to that the value they have gained since and the result is there are definitely fakes out there
At least in this case we are working from a picture, so that eliminates some of the vagaries
It does leave plenty of scope for speculation and imagination, It's worth remembering what shaky ground we are on assuming anything
Mind you, it does leave me free to choose what colour to paint the front panels on my WNW Pup, if I ever finish it. I doubt anyone could prove me wrong

Richard