Confusing earth wiring

When buying Vida, our surveyor included concerns about the earth.

We knew that the engine was "earthed" by a jump lead to the stern tube (and the jump lead was very rusty).

I've just found these wires connected to the anode that is bolted through the hull.

Quite a collection! We have green/yellow, back, blue and red!

Hardly surprising that the earth wasn't working!

#Oops