IDK about the stains but I saw a remnant at a local store that had been sitting outside for some time and the top was a different color than the bottom part shielded from the sun by other remnants.

The color fades when exposed to direct sunlight. Part of my counter is next to the window with a lot of sunshine coming in the morning, that is why I abandoned the idea right away though I already had a pattern picked out.

Don't know if that helps any.

I've had my Silestone countertops since April of 2002 and have never had any staining or bleaching. I do have a few small chips on a well used section of it. I can't see them from above but can see them when I look across it. The front edge around the undermount sink feels rough to the touch though it still looks fine.

I think some people have written about the colour changing in light coloured quartz - I have Cambria's Bristol Blue (dark blue) and over 3 or 4 years now have had no change whatever, even though part of it is in direct sunshine.

We spill tomato, red wine, olive oil, lemon juice, balsamic vinegar, whatever all over it on a regular basis (well, not intentionally). It's never, ever stained.

No chips in mine either.

"Quartz" is made out of quartz stone dust and resin. Yes, the resin yellows over time and exposure to UV. It shows most in the light colors, which is why they try not to install them outdoors.

There is a good previous thread on staining.

It is theoretically possible to stain the resin, and the right chemical that does not belong in a kitchen could even stain the stone dust, but in general spots will come off.