What Does ‘Colorful Formal’ Mean?

What is “colorful formal”? I keep seeing it on invitations for events this summer. Where did it come from, and what does it mean I should wear? — Alice, Waban, Mass. “Colorful formal” is yet another newish dress code term that, like “creative black tie” or “razzle-dazzle” or “mountain elegant,” actually makes the recipient of…