Steve,
I did quite a bit of air brush art for the WWF, World Wrestling Federation, back in the day and the WWF, being a large corporation, they had many guidelines I had to follow with managing their colors especially if the colors went to a print medium. Not just colors but, in some cases, few actually, design and composition also.
In the trade it's called "color management." Yes, it can get complicated especially in the print medium when dealing with different types of printing equipment. Much much more difficult today because there's more contraptions that share color imagery. Digital cameras are just one example and monitor color accuracy is another. I'm keeping this simple, a little long, but simple.
I have to say this. Sure, I never entered a model in a scale contest or put together scale documentation for a model, but I know color management and I know this well.
You have to as a professional if you do art for corporations like the WWF, Budweiser and Volvo. I did art for all three including many advertising agencies dealing with their specifications with color management, over many years. You simply have to get the color correct. Yes, they all paid me quite handsomely. They paid for my sports cars and aircraft over many years.
So, I view your issue as a simple one.
Document all colors as best you can, color chips, and possibly back this up with letters of authenticity where possible. Use this acquired information, color chips letters, etc.
Paint your model based on the documented information you have acquired to a tee, that is, as exact colors as possible which were used on the aircraft. "Perfect" in fact based on your research and your file full of great accurate stuff!
If a Judge doesn't realize color photos taken at different times of the day or interior lighting, renders variation in color, same with printed copies, then he shouldn't be a Judge. Or she. PERIOD!
I may be wrong, but I strongly believe your job isn't to educate the Judge, but to put on "display" an extreme presentation which is as accurate as the full scale aircraft you're modeling, including colors.
I hope this helps.
Got photos?
Charles