When the witch resurrects her ex-lover from the grave he is a zombie and is green. If he was in the grave for over 100 years his skin tissue would have allready decayed, leaving nothing more than bones.
well you know he WAS killed by a witch. perhaps she decided that he wouldn't rot like other ghosts, and in this way be able to help her in the future? or perhaps the same spell that brought him from the grave repaired his ... uh....rot? i don't know i'm just grasping at straws...
Remember this is a kids fantasy movie, witches flying on broomsticks don't exist and there are no talking "ghost" cats in real life so who really cares what the zombie looks like.