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.
Use this color coding and days to create and manifest what you most desire. Monday is a yin or receptive (female) energy the colors are White, silvers, Creams and Light Greys. These are the colors for women's mysteries, protection, emotions, dreams, clairvoyance, home, family, medicine, female fertility, messages, theft and voyages.