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.
Red. Red is the color of fire and blood, so it is associated with energy, war, danger, strength, power, determination as well as passion, desire, and love. Red is a very emotionally intense color. It enhances human metabolism, increases respiration rate, and raises blood pressure. It has very high visibility that s why stop signs, stoplights, and fire equipment are usually painted red. In heraldry, red is used to indicate courage.