For one, all of the "Official" Fushigi Yuugi repro 
cels have that blue-green colored mat around 
them. There are three sets of Fushigi Yuugi 
reproduction cels so far -  one is hand-painted 
repros of hanken cels (very expensive and 
about impossible to find anymore), one is the 
first set of TV repros, which you can find at 
http://www.omochabox.com (search for 
Fushigi Yuugi) and one is the second set of 
FY TV repros, which I personally think are the 
nicest. Those have been popping up at 
Usagi's House and Anime Game once in 
awhile but so far I haven't seen anyone else 
selling them.