I use a Scart to Component converter for my Genesis. When I first got it I tried fooling around with the color knobs inside the converter, and I got it set up pretty good, but there still some color bleeding - especially bright reds. Eventually I stopped trying to adjust it anymore, and I think it looks pretty good. Maybe I'll use this program to fine tune my TV a little more since I have an Everdrive.
However, I did notice that when I compared games from the Genesis to the same games on Saturn compilations, the Saturn (via S-video) looked much better. I don't know if the Saturn somehow enhances the colors, but the Genesis cartridges looked noticeably inferior to the Saturn when I had them playing together. I use a switchbox to connect my systems, so I simply ran the Genesis and Saturn at the same time and kept switching back and forth for comparison. Castle of Illusion seemed to have the most noticeable improvement when played on the Saturn.