What color combination indicates a channel marker that is safe to navigate?

The correct answer is based on the well-established navigation rules that help mariners understand waterway markers. A channel marker that is safe to navigate is indicated by having green on the right and red on the left when returning from the sea. This color combination corresponds to the IALA (International Association of Lighthouse Authorities) buoyage system, which is widely adopted in maritime navigation.

When approaching from the sea and heading towards port, the green markers signify the starboard (right) side of the channel, while the red markers indicate the port (left) side. This system provides critical information to boat operators, ensuring they stay within safe navigable waters and avoid hazards.

Contextually, while all red markers do signify specific navigational purposes, they do not universally denote safe waters on their own without reference to the accompanying green markers. Similarly, although red on the right and green on the left is often used in discussions about leaving port, the phrasing is not applicable when discussing the direction of navigation from the sea. Yellow markers further have distinct purposes for caution or information, but they do not indicate a safe channel for navigation.