a pic would be needed but if its eating and still moves about then its more than likely ok, its not unusual to see color variations in them......what are you running for lights???
bubbles are somewhat hardy and they often change shades of green and their tentacles can go from stringy like spaghetti or really bubbly and plump randomly.
not much you can do for any nem besides make sure its eating getting light and its important to always maintain clean water with no salinity drops or temp rises
cheers