I always thought of it as weakening him mentally, just as green weakened him physically. In that context, too, loss of inhibition makes sense.
As for the comics question, yes. In the comics, each piece of red K, created when green K passed through a mysterious "space cloud," had a different effect on Superman. Effects were generally temporary (almost always wearing off within 24-48 hours), and once he was exposed to a given piece, he would thereafter be immune to it (which is not what we saw on the show). Different pieces aged him, made him really fat, turned him into a giant ape, and all sorts of really random stuff.
Of course, red K was wiped out of continuity with Crisis, so it didn't officially exist when L&C was on the air. I think it's been written back in since, but I'm not sure.
Paul
