Hulk's skin. Prince Namor's swim trunks. Moondragon's costume. Among the Defenders, the color green was inherently suspect. Heroes in green had a tendency to change sides and turn on their allies.
Underlying the dualism of each of these green-clad characters was a recurring frustration with puny humans, surface dwellers, or mere mortals. Through this lens, it's not surprising that the New Defenders refused to let Frog-Man join their team (New Defenders #131).
Perfectionistic to a fault, Moondragon long considered herself morally beyond reproach (Avengers #149; #211; #219-220). When Odin felt Moondragon finally learned humility, he removed the headband that limited her powers (New Defenders #139). Within comics, changing costumes often symbolizes a change of heart. True to form, Moondragon temporarily replaced her green costume with a black-and-white costume (#140).
But the lesson of humility was short-lived, as Moondragon ultimately betrayed her teammates just the same.