Numbers 4

Why did God command that some of the sacred vessels should be covered with blue veils and others with purple veils?Only the veils of the more precious vessels were blue. The color suggests the sky. For this reason God commanded the objects behind the veil to be covered with blue tapestry but the objects outside it with purple and colors like it. For the sky is not subject to punishment, but the earth is punished for transgressions of the law. The color purple signifies a kingdom. The kingdom of God is divine, without beginning and indestructible. Hence the objects outside the tent were covered with veils both purple and blue. When the household of Kohath exercised their office, the law commanded that the priests should first enter the sanctuary and cover the ark and the other vessels with the veils already mentioned. Only then would the household of Kohath transport these objects, lest they lay eyes on things that are sacred and secret and that would destroy those who see them accidentally.