I got the question: How do I pick the colour for my foundation?

Foundation is the product most people struggle with finding the right colour of. When you try to find a colour, don't just try it on your hand in the store, you won't get it right 98% if the times. The colour of your hand, or even the back of your wrist isn't the same as your face.
What you do want to do is to try it on your cheakbone, right where it meets your neck, it is after all there it needs to match, one of the worst foundation fails is to get a line where the foundation ends. Don't try just one shade, try two, three or even four, to make sure you get the right one. Then go outside, the store lights will give you a totally different experience. Wear your foundation smears for a couple of hours in different lights, does it look different in daylight than it does at your desk? What you want to look for is a shade that blends with the colour of your neck, make sure it doesn't get darker, you usually have more colour your face than on your neck. If you're not sure, go one shade lighter rather than darker. If you feel pale, you can always get some colour with a touch of blush or bronzing powder. You can also ask the store for a free sample to take home, that way you can be totally sure before you spend any money.
Our complexion either has a warm or a cold tone, so does foundation. If you've got a pink skin tone and use a warm foundation colour, you will look orange, the other way around you will look sickly. L'Orèal True Match Foundation presents all the colours in both warm (W) and cold (C) tones, with matching concealers and powders. I'm a natural pale, redish blonde and wear C1.
Remember that you often need a darker tint during the summer and lighter tint during winter. A foundation should be thrown out 24 months after it's opened.