First examine your skin in natural lighting to determine your complexion: fair, light, medium, tan, deep. Concentrate on the skin around your jaw line. Look at the color of the veins on the inside of your wrist. This is a quick way to figure out if you have a warm, neutral, or cool skin tone.
To test how close the shade is to your natural color, apply the lipstick
only to your lower lip. Compare that shade to the upper lip. If the shades are
drastically different, you need to keep looking. Dark shades will actually make
your lips look smaller, while lighter shades can add plumpness. Lipstick with a
matte finish can also cause lips to look thinner, while glosses and shimmery
shades can make them look fuller.
Remember that your undertone and complexion will help guide you, but they
aren't the be all end all of choosing a lipstick color. It is important to try
on different shades and, ultimately, choose what you feel looks best. If you have a deep complexion, try
browns or purples like walnut, caramel, plum, or wine. Cool undertones should
look for ruby and wine colored reds. Warm undertones: try copper or bronze.