One of the hazards of a light colour interior. Look great as long as they are immaculately clean. Nice job BTW, It always strikes me as a little strange that folks will spend endless amounts on special this and special that cleaning products, when a good old bottle of 1001 is just the job.
I too had a mucky speaker cover that had dirty engine oil marks on it from where a friend brushed it with dirty hands as he retrieved something from the door pocket for me..
I used a foam upholstery cleaner from a car accessory shop..
It worked perfectly.