In order to be consistently accurate with application of the caution flag all that's required is the red. Stop the race, inspect the racing surface, the walls / safer barriers and any cars that appear to possibly be shedding pieces. Identify all discovered debris in order to ascertain its potential for damage or injury, photograph all of it and communicate findings and photos to race control.
A brief committee meeting will result in the correct decision every time. Implement by instruction to the flag person and a press release to all credentialed members of the media, two Facebook entries and 3 or 4 Tweets.