Once you met a few hostile Greens, it is easy to take Greenness (disproportionately) as an evidence for hostility. After all, they are Greens, so they must agree with everything those other Greens said; they are just strategically less open about it.

If your group happens to have a Blue majority at given moment, and you find more people like this, you can organize a Blue takeover of the group by declaring a fight against hostility, and by specifying Greenness (and defending Greens) as one of the symptoms of hostility.