It would appear that you're right. I mostly noticed the sky, rock color and Obi-Wan's cloak color being starkly darker at the end of the scene. But notice how Luke's left arm's sleeve is more towards his elbow once he falls and at the middle of the clip when Obi-Wan bends down the end of his sleeve is at his wrist. When they help C-3PO up Obi's hair was obviously recently combed and his hood has been flattened down. Much different than the middle. So it's obviously two different takes, and possibly a different day with different lighting. That could have been a reason why it looks so washed out compared to the rest of the scene.