A/C charged - Green liquid and noise

I just serviced the A/C. It's a converted system to 134a by a dealership. I changed the o-rings at the compressor. I changed the accumulator/drier. I vacuumed for 45 minutes and turned the pump of to check for leaks. It held the pressures for 30 minutes. I filled the system, blows cold (about 60 at idle, 49 driving). However, when i shut the car off with the A/C on, a hissing (sounds like air being released from a tire) lasts about 10 seconds and stops. Shutting the car off with A/C off it does not make this noise. The lower line from the condensor to the lower line leading into the firewall shows a little lime green liquid. I wiped it dry, check it a couple of days later, and had a drop or two on my finger. Is this noise, liquid normal? Is it the pressures equalizing or do i have a leak (but it held pressure for 30 minutes)? Thanks,