okay, you are really getting into it.
if you know the hex value for the color bit of the skin tone you are looking for and examine files for that bit and reconstruct the file where the bit was found you may be able to recapture the picture.
easy for standard picture files but steg makes the task even more difficult.
however, if you are this far into it you should be working more with one of the law enforcement organizations and less with us here.