Yeah, the blue path is effectively the "sharing" path, but it's different because the couple are the only ones in on it. As far as the other guys know, they're doing it behind the MC's back without his knowledge, so they think FMC is cheating/they're stealing her. The FMC is fully on the same page as MC though, so she only goes as far as she has prior permission to, but tends to push those boundaries a bit in order to facilitate going further the next time. She will return to MC and tell him everything after the fact, whether he was watching it or not.
The red path is effectively the "cheating" path, because MC said he didn't want to know about it/didn't want to continue with the teasing games. He knew that FMC was going to continue doing stuff, but wanted to see how far she would go (and wanted her to go there), so again it's different to a normal cheating path because MC is fully aware of most of what is going on, and wants it to happen - he follows FMC and watches a lot of what she does, only she doesn't know, so he can't get as close and sometimes therefore doesn't see everything. On this path, not only do the other guys think the MC is unaware, but the FMC also thinks he is unaware (at least mostly so, anyway). So she doesn't tell him what has happened, and actively lies, saying she was doing other things or just saying nothing happened, even when MC (unknown to her) actually saw what happened. So I suppose this one is closer to a "willing cuck" path, it's just that FMC doesn't know about it.
The Erick blowjob, as confirmed in a couple of other posts, is a natural event on this red path, though it's kind of different in tone to the other stuff. Even on this path, MC is all for FMC blowing Bruce, but when it comes to Erick, he's less okay with it, showing some dread when he realises it could be what he's about to catch happening.
