Dale & Paulette,
I had a green marble floor in my previous coach, it is softer than granite and that is why it scratches so easy. The best way to make it shine like the day it was installed is to have a professional re-finish it.
I had a master marble finisher do the job. He wet sanded the entire floor with 5 different grades of sand paper; the last finer than the first. When he was finished it was like a mirror. The cost was about $550 and it took him about 4 hours. I thought it was well worth the money.
I am sure that some of the guys on the forum could tell you how to do it if you would like to do it yourself.
If you contact a retail marble tile vendor, I am sure that he can put you in contact with a master marble finisher.
Good Luck!
P.S. Liquid polishers don't work; at least, I never found any that did.
Tuga & Karen Gaidry
2012 Honda Pilot