Monocolored creatures can't block this turn.
A monocolored creature is exactly one color. (Colorless creatures aren’t monocolored.)
No monocolored creature will be able to block that turn, including monocolored creatures that enter the battlefield after Awe for the Guilds resolves. A creature that’s monocolored when Awe for the Guilds resolves but somehow becomes multicolored before blockers are declared will be able to block.