I had a similar problem with my PS2. Component looked perfect but RGB through SCART was green. So Bucko told me to go into the PS2’s system configuration and change it from YPrPb to RGB. This fixed the issue.
Next, 480p mode didn’t work, the OSSC simply said “NO SYNC” and the screen was blank (black). Bucko told me to manually change the OSSC into RGsB mode when the PS2 outputs 480p (press the input button to cycle to it). Now 480p looks perfect!
I hope this information saves someone else from looking like the fool like I did. :$