There's also a contrast in the sky in the scene where the ronto was replaced in the distance. It's the scene where Luke and co. arrive outside the Cantina and are getting out of the landspeeder.
Also, in the scene where the rebel fighters are leaving Yavin, the blue sky looks like an animated blob where the fighters are taking off.
I've noticed the sky contrast in the dewback seen as well, but other than these three I haven't noticed any other sky issues.