Different cameras record at different quality. Plus lighting and angle make huge differences. Then there is the processing (contrast, brightness, etc) of the actual footage being done when it is copied over to Video and DVD.
For example, here are 3 different versions of Dorian from the same contest 1995 Mr. Olympia. The 1st one is from a Video, and the 2nd and 3rd pics are from two different DVD's. Big quality difference in all 3. Dorian is Brown, Yellow and Red. Just go with the more realistic one in my opinion. The same goes for Ronnie lol.