USN LANDING AID?

Can any one tell me the reason why U.S. Navy carrierbourne types have, somtimes in an oblong box, 3 coulered lights. Always, red, green, amber, but not in that order. The box of lights is most often on the nose wheel leg, or on the nose wheel door. But always a part of the nose undercarriage. THANK YOU IN ADVANCE. LFDD.