Would it be possible to gain some sort of color coding ability? Basically, let hosts select a few colors to define how their guild should see others? This way guild leaders could let members know how to act towards certain situations. For example, my guilds might have blue for allies, yellow for do not sink, etc. By offering the host a rainbow, each guild can detail what their specific colors mean. This would not block guild actions (could still attack "allies"), but it would permit distinction between guilds. This could serve as a reminder to "attack on sight" or "leave friends alone".

Also, the most common form of color blindness involves red and green.