Can someone help me understand the PS2 controller port circuit?

[musica.cards]

I'm trying to build a little something, but I don't quite understand what I'm seeing when I look at the controller (and memory card) port. I'm using a spare port right now, but I'm trying to determine the input part of the circuit.

[guff]

cut the blue wire

[musica.cards]

cut the blue wire

What do you mean "cut the blue wire"? They're all blue wires