What color is used for the topmark of an Isolated Danger Mark?

The topmark of an Isolated Danger Mark consists of two black spheres, which serve a clear and distinct purpose within the IALA maritime buoyage system. These black spheres indicate that there is a navigational hazard that is isolated from other dangers, signaling to mariners that there are safe waters surrounding the isolated object. The black color of the spheres is easily visible and straightforward, allowing for quick identification under various sea and weather conditions.

While other colors and shapes may be used for different navigational aids, the two black spheres specifically identify the distinctive nature of an Isolated Danger Mark. This visual cue aids mariners in recognizing the isolation and the necessity to navigate safely around the hazard. Understanding this specific marking is crucial for safe navigation and to prevent potential accidents in marine environments.