(like) a red rag to a bull an object：utterance, or act which is certain to provoke or anger someone.
a red herring something：especially a clue, which is or is intended to be misleading or distracting.
green about (or around or at) the gills ：looking or feeling ill or nauseous.
scream (or yell) blue murder ：make an extravagant and noisy protest
born in (or to) the purple: born into a reigning family or privileged class.