What Color Is Your Helicopter?

Wiki:

The concept of black helicopters became popular in the United States militia movement, and in associated political circles, in the 1990s as an alleged symbol and warning sign of a conspiratorial totalitarian military takeover of part or all of the United States. Rumors would circulate that, for instance, the United Nations patrolled the US with black helicopters, or that federal agents used black helicopters to enforce wildlife laws. The concept springs from the basic truth that many government agencies and corporations do use helicopters, and that some of these helicopters are dark-colored or black. For instance, dark-colored military helicopters were deployed in the standoff at Ruby Ridge.
The phrase "black helicopters" is also sometimes used figuratively to ridicule conspiracy theories in general (see below).
In the United Kingdom, a similar phenomenon known as "phantom helicopters" has been reported since the mid 1970s. This concept relates phantom helicopters to UFOs and alien invasion rather than to martial law.
The issue was first popularized in the early 1990s by Mark Koernke (also known as Mark from Michigan) in appearances on Tom Valentine's radio show and in public speeches which were widely circulated on videocassette, and shortly thereafter by Linda Thompson in her film America Under Siege. In Alex Jones' film Police State 2000 unmarked black helicopters are shown flying low in surprise urban warfare training missions with Delta Force operators and foreign troops.
Two books on the subject: Black Helicopters Over America: Strikeforce for the New World Order (1995), and Black Helicopters II : The End Game Strategy (1998), are from the now-defunct Illuminet Press and were written by Jim Keith.
The greatest media attention to black helicopters was most probably paid in February 1995, when first-term Republican northern Idaho Representative Helen Chenoweth charged that armed federal agents were landing black helicopters on Idaho ranchers' property to enforce the Endangered Species Act. "I have never seen them," Chenoweth said in an interview in The New York Times. "But enough people in my district have become concerned that I can't just ignore it. We do have some proof." Chenoweth made the charges at a press conference without ever consulting with the Department of the Interior.
The U.S. Fish and Wildlife Service, which enforces the act, says that they do not own any helicopters nor have ever used any in Idaho. The only green and black military helicopters known to be used in Idaho are used by the National Guard. Black helicopters without FAA-required running lights are regularly used by the drug interdiction office of the DEA. In addition, most U.S. Army helicopters (such as the Black Hawk) are finished in a very dark chocolate or olive matte paint.
Black helicopters have also been reported in the areas where cattle mutilation has been reported. The black helicopters theory resonates well with the belief held by some in the militia movement that troops from the United Nations might invade the United States.