bb: Welcome to the joys of the W116 and the M110! May you get many years and kms of pleasure out of it.
Without a doubt those seats are MBTex - almost indestructible, far more serviceable than leather, and more flexible so, in my opinion, more comfortable, as the leather becomes hard, unyielding, and shiny with age. I have MBTex in all but one of mine, and even in the 42-year-old it's in amazingly good nick. And it requires no more care than the occasional wipe over with a damp cloth.
Warning: do NOT, under any circumstances, use Armorall on your vinyl: certain and quick death will ensue from the application of that muck. Best treatment for the dash-pad vinyl and doorcard trim is an occasional application of vaseline / petroleum jelly or baby oil. I use petroleum jelly.
Your interior colour is Bamboo.