I know there is a dark side corruption effect on your character but is there an affect if you choose light side? Also is it possible to change your alignment late game or is it a lost cause?

No your face won't change when you are light side since canonically using the dark side of the force corrupts the user hence why they look corrupted and jedi look normal and yes you can change your alignment it will simply take a lot of flashpoints or gaining points through the diplomacy crew skill.

I don't know if there is a light side complexion effect ingame, but it is possible to change alignment. The sith warrior get two opportunities to reverse his alignment

which completely reverses it, light to dark and vice-versa.

 

You can also change it the hard way, by choosing the alignment you want, but if you leave this too late it won't work, ie if the choices you can make are less than your current alignment, but you won't know that unless you try. I would say if you have entered chapter 2 then you are probably better restarting.

 

Also is it worth it, the Jedi Consular story doesn't change, but the Sith Warrior story does, I would research how much your story will change, via the forums here and google. And if it's just the complexion, then you can turn it off.

The Sith Warrior can't totally reverse their alignment in that one conversation. They just get a big boost to lightside or darkside points. Edited December 10, 2012 by OldVengeance

You can gain the opposite alignment points enough to go fully the other way even if you're already 50 and maxed out. Run Flashpoints and/or do Diplomacy missions (requires Diplomacy skill of course). I think the flashpoint LS/DS gains may have limits on repeat ability... like once per day or something like that but otherwise it should work.

Running Flashpoints and Diplomacy missions can easily make up for early/mid level dark/light depending. Also once you hit Light/Dark V you can still go the other way it doesn't lock you into that.

I must criticize, that Dark Jedi tier V, still look meditating, and Light Sith tier V still have 'channeled hatred' to recover.

 

It should be a possibility, when you reach Light/Dark V., that Sith will has powers like a Jedi and vice versa

The only canon confirmation of a light side effect on the body was the Exile and that was just luminescent blue eyes and very pale white skin.