The only reason the birds would be marked DQ is if they had some major fault. For instance, a black bird with white feathers...and the breed was supposed to be completely black.
Or a bird with yellow legs and the legs were supposed to be shale or willow colored. Mind you, these are just random examples, there are MANY others for each breed that is specific.
In 4H shows and in FFA shows it may not matter, as the kids will probably only have the "production" class, the "meat" class, the "rainbow layer" class, etc. I judge all of these shows...and it's pretty much a participation thing, but there has to be a winner in each area.
When it comes to the breed showing part, I judge hard. The year before, there was not a single bird that I would not have disqualified. This year when I judged, I was having difficulties in selecting a champion and reserve champion.
There is always hope, but if the bird is supposed to be a buff orpington and has a columbian pattern of some sort, the judge should DQ. Depending on how the judging is done (APA sanctioned show), the judge may or may not mark the birds NSQ or DQ them based on the fact that they're not SQ. You should contact your local fair board and see how they plan on judging this year.