I was always wondering what the lights on the side of certain firetrucks near the drivers door. There are 4 lights that look like marker lights and they are usually green, blue, yellow, and red. A great picture is on the side of Engine 19-2-1 from Mahopac Falls. There is a great picture on the website!
http://www.emtbravophotos.com/SpecFeat/MahopacFallsFD.html