PAL consoles will output RGB through the analog AV connector. They lack s-video, however. I forget if they have the digital AV out or not. I know that someone tried to get VGA through the RGB output, but it didn't work.
NTSC consoles will not output RGB through the analog AV port, but they do have s-video. You can get VGA or RGB by modding the component or d-terminal cable that connects to the digital AV connector. From what I have read, the output will be 31KHz VGA in progressive scan 480p mode, and 15KHz RGB otherwise. I believe the sync is separate H/V like VGA.