Copper builds up far less surface fouling than most metals, so cleaning is usually simple: the light deposits that do form can generally be wiped away.
Copper and copper-based alloys resist fouling because copper is toxic to organisms such as algae and seaweed, which makes them well suited to subsea applications.
Copper and copper-based alloys also provide excellent corrosion resistance through a passive film that forms when the surface is exposed to oxygen. At first this gives the copper a light pink appearance.
Over time the passive film develops in thickness and composition, taking on an increasingly dark green shade. Removing this patina forces the copper to re-passivate to protect the surface, and the colour-change process then begins again.
You can seal or coat the surface to keep the original appearance and colour, but that works against one of the main reasons for choosing copper in the first place: its inherent corrosion resistance.