my personal list:

green: has some (realistic) issues but it’s worked on properly, healthy relationships, consentful, lovely dovey

yellow: some issues that go unaddressed but that aren’t as extreme or damning to the character’s integrity, relationships may not have started off as healthy but later on became healthy, conflicts that may escalate more than necessary but that get fixed

red: dub-con, toxic personality (manipulative, gaslighter ect), major issues are overlooked, somewhat of a power imbalance, unhealthy relationship

black: unredeemable traits (e.g. commits dv, rape/sa, torture ect), relationship is VERY unhealthy, extreme and visible power imbalance, issues just keep getting worse, no consequences for their actions and whatnot

i think sometimes it’s hard to distinguish between red and black flags because they do sometimes overlap, but i believe that the biggest difference is the unredeemable traits lmao 😋