I have a very serviceable sofa, light gray that has become soiled. I remember seeing a product that was dye in an aerosol can, but this was a while back. Do you know of any such product that is on the market now?
I am unaware of any product like this. It is possible to spray on fabric dye, but with upholstery you run into the problem of not being able to easily rinse out excess dye. I have seen upholstery spray painted on Trading Spaces, and I believe that they use ordinary latex paint. You can also brush paint onto fabric. Go to Home Depot and consult with them about paint on fabric. The Trading Spaces website has some interesting stuff on painting canvas which can then be used for slipcovers. Since slipcovers are so much in style right now, this might be the easiest and most elegant solution to your gray sofa. If you want to get really creative, you can dye or paint the slipcover fabric. Have fun!!