Hola Hermana!
I've thought about that on ocassion too. I think there are quite a few reasons why NPC & IFC GLOs don't always use the official colors.
-to show school spirit by using school colors
-to distinguish families, each family has thier own pattern of letters
-to express your personality, I have sisters who have letters in hot pink leopard print!
-display your favorite colors==the ones that aren't the GLOs colors
-as a way to be able to wear them more often==what if your colors clash with your fav shirt? But you still want to show your pride?
I also think since there are far fewer FRIENDLY rivalaries (sp?) between NPC/IFC GLOs than between many MC GLOs; that there isn't the whole "I'd never wear THEIR colors!" mentality. Just my opinion.