Can you wear foundation on top of this?

You can definitely wear foundation over this. Depending on how intense your redness, you can wear alone or for more coverage, add your favorite foundation.

How do I know if the color will match my skin?

I had tried my daughters before i purchased it. Her skin is light and mine is medium. We both use our mineral powder makeup over the top of the bye bye coverup, this seems to even out any uneven color. I love it, it covers even my brightest red areas from my roacea breakouts and doesn't irritate or break me out more. It even feels soothing to the inflamed areas.

I have very red cheeks (broken capillairies from HBP). I discovered a tiny bit of Bye Bye covers it! Is this the same product or better?

I bought this because I also have broken capillaries, it was an absolute waste of money, it did not cover at all. I bought it because people were raving about on the internet, its too expensive, I ended up buying Revlon colorstay, it was $14, I mean its okay, you can also try Dermablend, which I think I'll be going back to. Dermablend is a little heavy, they have light version also . Don't waste your money on Bye Redness, it did not work for me, hope this helps.