A320 version of Airbus hydraulics
All three systems work regularly (whenever there is demand) to maintain 3000psi.
Each control surface or hydraulic user has a primary hydraulic source and some systems have secondary or tertiary sources.
Spoiler no 3 has blue only but the rudder has all three sources whereas the ailerons are powered by the green and blue systems, with the left aileron having blue as it's primary and green on standby and the right aileron having green as it's primary and blue as the standby.
The hydraulic architecture diagram in the back of the QRH explains a lot of it.