[Andy Brockway]

If you are talking about the SMC valve then black is for ground and red would go to a spike relay. You could connect both to the relay if you have no need to use the other output on the relay.

If you are talking about the Festo valve, you need to wire it yourself. The connector is included in the box. 1- Negative(ground) 2- Positive (spike) 3- not used.