Far too much ambiguity. "Red flag" and "white flag" are also idioms (probably more common than "black flag"). There are red beans, black beans, and white beans. There are red, white, and black hat hackers. There are black and white keys on a piano. "Heart" is more associated with red than black (think playing cards). So even though it was apparent early on that three of the categories were "red, white, black", this hardly narrowed it down at all.

I also didn't feel like the idioms with "all over" worked for me, but this might be regional / cultural.