Why are certain buoys colored differently?

 title: 'A cross-section of a multi-story building showing various rooms and provisions.'

Buoys are colored differently to offer a means of distinction[1]. The text specify that starboard-hand buoys shall always be painted in one color only[1]. Port-hand buoys, on the other hand, shall be painted of another characteristic color, either single or particolour[1].

The source notes that green is for marking submarine telegraph cables[1]. It also adds that wreck buoys in the open sea shall be colored green, with the word 'Wreck' painted in white letters on them[1].