Supposedly, the color timing was changed completely for "Alice in Wonderland" (someone posted comparison screenshots from another thread) and the coloring seems to have been changed for the "Beauty and the Beast" DVD and Blu-ray. Most recently, "The Little Mermaid" had a few changes, including moving "Walt Disney Presents" to different shot, removing a cross fade, transposing two shots (which Disney corrected and offered a replacement disc) and "cleaned up" some rough animation. Arguably minor changes, but many of them didn't go unnoticed to die hard fans. I'm sure there more examples of Disney altering films from how they were released theatrically. However, their restorations are mostly faithful. I can't comment on any of their live action films.