The carpet is black, just give it a once over with a vacuum. I do the same sort of thing with a cream carpet and just a quick vacuum when I can be bothered and pulls the muck right out. Good fun hauling around bags of horse turd, took ages to clean it all up. That straw gets everywhere.
Should see a tractor dealer down the road from here though, they use L322s as recovery vehicles and they take some abuse. Farmers use their L322s as farmers cars, they are always caked in mud, constantly pulling all sorts of farmer type loads around the place. Tell you something for free, I wouldn't buy a second hand one from up here.
Charles Spencer King would be proud though.