I use dye from malco. Do you have a pic of your carpet? I can prolly tell you what color it is. If it looks like dark pewter, the color of dye is most likely "Tawney Grey" but I'd have to see it. Dye is the only way to go. I pull out seats and trim to expose 90% of the carpet to dye it. Yesterday I dyed a repo'd Cobablt carpets black. The carpet was originally tan and the plastics were black and tan. HAHA. Tawney wouldnt hide the stains, and Charcoal didn't look good, So I gutted the interior and just changed the whole color. What a job that was! LOL. Looked better than it would have from the factory cause the black carpet looked better with plastic's colors.
Anyways, if you clean your carpets real good. That also includes wet scrubbing with some sort of all pourpose cleaner, wait till they dry, and then make a nice uniform coat of matching dye, it will look nice. You could go to a local detailing shop and see if they would sell you a can of dye. Or just have them do it? They'd prolly charge you $20 or 25 to just do one floorboard. Malco's dye is $7 a 16 ounce can and it can usually dye all the floor boards in a car if the carpets aren't trashed. The main cost is labor and prep. If they are a good shop, they will tape off your plastics and remove any over spray. You will never know it was dyed.
