Like notaries, witnesses aren't generally required in order for a contract to be legally enforceable. However, each state may require special kinds of contracts (e.g., real estate deals, wills, and marriage agreements) to be witnessed by a third party in order to be binding.
McDonald's, apparently, use red and yellow because red=fast and yellow=hunger (hence fast food!). Remember also that meaning is what we create. It does not exist in the color itself and individual meanings may or may not exist in different cultures and individuals.
fast-paced - of communication that proceeds rapidly; a fast-paced talker; fast-paced fiction. fast - acting or moving or capable of acting or moving quickly; fast film; on the fast track in school; set a fast pace; a fast car.