By you sending me a small piece of the carpet and the color of the problem that exist. Yes what ever problems you have , just let me know of the other problems that exist and more colors will be provided.
Chemicals always exist in the carpet, no matter how long ago the problems began.
By using a carpet cleaning machine or a wet vac. It will neutralize the chemicals and accept the new color needed to solve your situation by color matching the spots. They are color fast meaning as long as the carpet spots are rinsed well the dyes will adhere to the carpet fibers. Yes but sometimes depending on how dirty the overall carpet is some of the dyes can be removed and may need to be touched up. A strong cleaning with excessive amount of cleaning chemicals can create this need.