You may not quite see the point in having a white foundation, especially as I'm not a makeup artist.  My makeup is for me.  The reality is though that I am SO pale (especially in the winter time) that most brands palest foundation is still too dark for me, so I decided that as I was tired of struggling to buy foundation, I'd just get myself a white foundation to mix with those that are a bit dark at times.  I ended up buying the MAC Face & Body in white online after trying to find exactly what I needed.  It's a pro-product so can't be bought in store but it was delivered pretty quickly.  The texture of Face & Body is very liquid, so it's easy to mix in with foundations and is not massively different from how some people mix a little liquid highlighter into foundations to make them more radiant.  I also find that this doesn't alter the texture and finish of most foundations, so it's not turning it into something completely different from the original formula.  It has been such a useful product for me, and as I don't need to use much, and not with every foundation, I know it'll last me a long time.  I'm sporting a bit of natural colour at the moment because it has been really sunny in Scotland for the past couple of weeks - but I'm talking now I'm less blue looking and the palest foundations of most brands now don't need lightened (finally a Chanel B10!).  I honestly would recommend in investing in a white foundation if you're very fair, it opens the door for trying foundations that previously have always been too dark, and you don't need to live your life constantly applying fake tan to make your makeup work better; which is what I used to do.  These days, I'm embracing the pale and interesting look; made all the easier with my white foundation.