NIVO, short for Night Invisible Varnish Orfordness, was a dark grey-green finish applied to British night bomber aircraft between 1918 and 1939. It was developed in 1918 at Orford Ness to help make planes less visible at night, with a sheen that blended in with moonlit water. NIVO was used on various bombers like the Vickers Virginia, Handley Page Hyderabad, and others. By the mid-1930s, it was found to be too reflective under searchlights and was phased out before the introduction of newer bombers like the Vickers Wellington.