Paul, actually having judged scale, its VERY easy to say the color is wrong,,
The key here is the documentation provided for judging with the model. If the builder presents a color sample, ( which he should) then the judge is compelled to judge the model against the color sample provided, unless the contestant has provided something horribly suspect, then the judge is required to judge based upon what is provided for color and markings. In fact, a judge is required to judge based upon the documentation provided even if he KNOWS the documentation is flawed, he still cannot use personal knowledge to overide provided proof.