The title is self explanatory. Although I'm not Ultimate, I know many players that don't like the default color Orange being for their chat. It gets bland and boring, and a range of colors to pick from would be better.
A wider range of colors could be used for Ultimate, and a narrower for Supreme. It gives players a chance to pick the color that suits them.
Or, we could just enable the '&' thing for colored signs in global. Although, take away the bold, italics, underline, and strikethrough. That would be too much.