So even on beaches red flags mean the same different things! 
Fuzzy meaning for relationships I understand but I really would expect there to be some consistent, even universal, flag language for swim safety. I wonder if it is state by state or even more variable?
Relationships are weird and fuzzy. I like the idea of yellow and red flags. But agree no one uses the former term. I think people mean different things by red flag. To some, it is an incompatibility of variable significance. Different diet, religion, politics, education, expectations, etc. it may be Seinfeldianly trivial (“He’s a ‘close talker’, She’s a ‘double dipper’) or very significant. Maybe a bunch of one person’s red flags is none or one for someone else.
I am sure some people also use a red flag to mean a dealbreaker. Many probably don’t. But a dealbreaker is a dealbreaker. I like the yellow flag term since it is clearer. This does not matter if no one uses it and everyone means precisely what they want it to mean, and assume everyone else understands or defines it the same way.
I guess I agree, but ….,
…race makes things complicated. I know.
I have a number of Asian friends, and the women have all said they’ve been on dates with white guys (and it was always white guys) who really fetishized the women being Asian. They found it creepy af and didn’t continue dating them when the fetishization became apparent.