Depends on the fabric, size, and depth of burn. If a small surface burn, but not thru the cloth, sharpies can do a reasonably good job at hiding the mark. If thru cloth, but not into cushion, you can take a small piece of fabric from a hidden area of the seat, create as clean a shape as possible, and fit the piece onto the seat like it's a puzzle, using a quality adhesive in a very thin layer,and applying weight to a flat surface(book) over the repair. If a mixed color fabric, scraping fibers from a hidden area can work, but use a clear adhesive,thin cloth, and iron the fibers flat. Smooth fabrics are much harder to work with, but I've seen all three methods used at professional new car dealerships. You can also spray the seat, with a fabric paint,see this frequently done to the top of convertibles back seats, which tend to fade. Dealer would have some, parts counter.