Stereo colour coding help needed please

[coach_carlos]

Looking for simple help,

My GF has just got herself an old Citroen Avantage ZX
Nice car, but the stereo has been cut out, I need to put a new one in but unsure of the colour coding on the wires, can you help?

1) Thich yellow wire with a small black square on it.

2) Thich yellow wire with a small Green square on it.

3) Thich yellow wire with a small (looks like) Brown square on it.

4) Thin redish brown wire.

Yours Carl