What color are the day shapes that vessels are required to display?

Vessels are required to display day shapes that are black in color as part of the regulations established to indicate their activities while underway or at anchor. The use of black shapes ensures they are easily visible against a variety of backgrounds, including both water and land, making it clear to other vessels what type of operation is occurring.

For example, a single black ball indicates that a vessel is at anchor, while two black balls displayed vertically indicate that a vessel is constrained by its draft. The choice of black for these shapes is crucial for visibility and ensures compliance with the International Regulations for Preventing Collisions at Sea (COLREGs), which help promote safety in maritime navigation by communicating the status and intentions of vessels to others nearby.