The FZ6/FZ1 and likely many instrument clusters use an internal CPU that processes data from the bike's computer (ECM). This is connected to the cluster via a data line signal that carries the tachometer, speed, coolant temp, error codes and CEL. You'll want to be sure the the alternate instrument cluster can process and is compatible with the FZ6 data line. The directional signal, high beam indicator, oil warning light, neutral safety light are separate wiring.
There will be more involved beside wire color codes.
Do you have data on the unit you're planning on installing?