It is possible that after their 1st successful plunder and before the next one, they have gone to remove their red name.

This can be done either by having someone from the different group attack them, or in same cases, they have a smurf/alternate account that they use to "attack" themselves to remove that red name. Same members in the same group are unable to attack them which you might have seem to imply when saying "If they intentionally make their group mates beat them up".

So once their red name status is removed, they will not get it again for the day, even if their 2nd and 3rd plunders are successful. Therefore, if you happen to see them battling a SS convoy in Konoha, and after they win, their SS convoy runs off and carry on, their name still appears white, as like I mentioned, you can only get red name once a day, which is removed after getting attacked 3 times.