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.
Green is a festive colour. In Maharastra, it represents life and happiness. Symbolizing peace and happiness, green stabilizes the mind; the colour is cool to the yes and represents Nature. YELLOW: Yellow is the colours of knowledge and learning. It symbolizes happiness, peace, meditation, competence and mental development.