The best way to choose colors to flatter your skin tone is to first determine what your skin tone is. Most women make the mistake that they are cool or fair skin toned. Only about 15% are true cool toned faces.
If you are fair or pink in color do NOT match your foundation to pink or red. Instead use something with a slight yellow undertone.
This will counter act the pink give a more youthful glow and the appearance of healthy more youthful skin.
If you have rosacea you want to counter that with a beige, neutral or yellow undertone.
For ebony skin a large percentage if women have what is called facial masking. This is areas of darker pigmentation generally found on the forehead and jawline. For this condition you will need to use two foundations to even out your skin tone.
You will need to match your undertone exactly because they are so strong ranging from golden orange to true brown. Always try to brighten not lighten. Apply at least three stripes of different shades to your cheek and wait to see if the oils in your skin will change the color. After a few minutes check to see which one matches the skin on your neck better. Once you've made your match you are ready to apply your foundation.