Here's a post asking that from a few years ago -

http://ths.gardenweb.com/discussions/2670497/is-it-possible-to-dye-or-stain-corian-countertops

I saw a company at a home show that sprays a coating over sinks, showers, etc. I am considering using it for my tub/shower.

This is the place I saw, but I bet there are other companies that do the same thing:

http://www.myrtlebeachhomeresurfacing.com/

There are DIY products you can buy, but personally, unless it was something I would have no problem replacing it things went wrong, I'd rather spend the extra and let a pro do it.

It is a waste of money to attempt to do anything other than replace. Considering that you can find a marble vanity top with undermounted sink at the nearest box store for less than $200, replacing is the only iption that even makes sense.

I had a tub done with the spray. It looked good for about a year. When I called about the warranty I was told I would need to "prove" I had not used abrasive cleaners on it.

I ended up replacing it and I was surprised when I got the quote how close it was to what I had paid for the spray.