Why are certain buoys colored differently?

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].