For the typical pool - I'd say any Cl level below 8-10ppm (preferably in the 3-5 range) is safe.

I don't think swimming in a green pool would hurt you, unless you drank the water. That said - I would imagine it's probably pretty hard to swim in a pool without getting at least a little water down your throat.

My preference, to be on the safe side is to ensure you have 2-5 ppm free Cl, proper pH (7.2-7.5) and water that is clean and clear. If the chemicals aren't right it's probably not going to be clear anyway.