Hi chameleonash. I totally agree with tenngal about going into a store to get matched by one of our Cast Members. As she mentioned, if you don't have a store closeby, the best way to find your best match is to look at the shade finder for Make Up For Ever, Cover FX and Bare Escentuals. Their shade finders will help you understand what undertones and complexion you have. Tenngal listed the links for Make Up For Ever and Cover FX. Here's the link to the Bare Escentuals shade finder: http://bit.ly/h14LCj. I hope this helps!
Answered[ Edited ]
The best way is to go to a Sephora store, or cosmetics counter near you, and have an associate swatch three shades that are close to your skintone on your neck / jawline (not your face itself). The one that disappears is the closest match. Guessing from online swatches is very difficult, even when the answer seems obvious, and you may need different shades across different brands. Once you find one match, you will still need to swatch shades if you want to switch foundations. Good luck!
It's best if you can go to a store and get one of their professionals to color-match you. However, if you don't have access to a Sephora or other makeup counter to get color-matched, then I would suggest looking at Make Up For Ever and Cover FX foundations because both brands have a "Shade-Finder" feature that you can click on to help you choose the correct color for your skin tone. Below are the links to:
Cover FX: http://sephora.com/browse/brand_hierarchy.jhtml?br
I hope this helps you.