The color grading of the Original Trilogy in 4K on Disney+ does look far superior to the DVD and Blu-ray versions, but it’s still not perfect to me. The lightsabers looks much better, especially when Luke is training with the remote on the Falcon. However, I have been very vocal about how much I hate this dreadful teal effect being applied to 4K remasters of older films, and it does stand out on the Disney+ versions. Revenge of the Sith and The Force Awakens seemed to have suffered the least in 4K remasters. I have not checked out Rogue One on Disney+ yet.
This also might just be me, but it seems like the music was mixed louder than the voices in Anakin and Obi-Wan’s duel in Revenge of the Sith.