hi! that actually happens to me too, just make sure to select all the frames in your animation window before making any changes to your coloring and you shouldn’t have that problem anymore because the coloring will automatically appear on all the frames. oh and don’t forget to put the coloring at the very top!
about changing it back… well i usually just go to my history window and delete what i did wrong
i hope my little explanation was helpful, let me know if it works! have a nice day :)