As flyhelico
"Dear A330-340
on the 320 bus, engine 2 power yellow hydraulic for parking brake(the handle on the pedestal).
once second engine is started(left engine # 1), the brake valve switches from yellow to green, and provide hydraulic pressure for normal braking."
This is correct. Also on the A330, engine # 1 started first as the 2 Hydraulic Pumps on it (Blue and green Systems) will allow normal braking and Alternate braking upon start up immediately.