this would be very contradictory to alot of star wars material, actually it would probably be contradictory to it all...but i could imagine a cool shot of anakins lightsaber turning from blue to red as after his transformation to sith, almost like red tendrils moving from the hilt downwards to form a red saber.

alternatively someone could just make a shot of palpatine handing anakin a new saber when he nights him, ie palpatines hands passing saber to anakins hands. could be done with just gloves and sleeves and the right coloured floor and lighting.

dunno where obi wan would get anakins old sabre from though, maybe a similar "hand" shot from the interior of padme's ship?

maybe ill suggest that to ady if he is still up for episode 3 rediscovered in 2018 ;)