Accuracy is actually a judging criteria (that would include colors),,,,,,,but, it is something like the 5th item on the list, with one huge exception.
Something like a Gloss Sea Blue Sherman, an International Orange Arizona or an Olive Drab F-4S gets thrown out before even looking at the glue seams and the quality of the paint job.
from the link in Wayne's post above, and in section
II-Contest Definitions and Judging
"Judging. Models will be judged for skill in construction, finish, realism, scope of effort, and accuracy. " (there it is, Accuracy is number 5 in the IPMS-USA list of criteria for judging)
Rex