Design of antennas, towers and accessory structures. Antennas, towers, and accessory structures shall be designed to blend into the surrounding environment through the use of color and camouflaging architectural treatment, except when the color is indicated by federal or state authorities such as the Federal Aviation Administration. Every antenna, tower, and accessory structure shall be a neutral color to be in harmony with and blend with the natural features, buildings, and structures surrounding the antenna or structure; provided, however, that directional or panel antennas and omnidirectional or whip antennas located on the exterior of a building that will also serve as an antenna tower shall be of colors that match, and cause the antenna to blend with, the exterior of the building. Accessory structures will be designed to be architecturally compatible with principal structures on the site.