Summarize:

If you have fair skin, you may be tempted to pick a tan nude. However, that can really wash out your face. Instead, pick a nude that has a hint of pink. It should still be very soft, but it will help keep you from looking too pale. If you're not totally fair but still light-skinned, you can go a bit darker. If you pick something too soft, your lips won't have any definition. Pick a light pink or beige with enough definition to distinguish your lips from the rest of your face. If your skin is in the medium range, try a more golden hue. Make sure that the color you choose is slightly darker than your skin tone, so you have definition. In addition, try not to pick something to heavy, texture-wise. If you want slightly more color, you can go with a peach undertone. Salmon can also be an appropriate color. Often, if you try to pick a "nude" for darker skin, you'll choose something that's too light. Make sure that the color you choose matches your skin tone or is a bit darker. For a bit of shimmer, go for a bronze or gold undertone. Look at your complexion to see if you have more cool bluish undertones or warm yellow undertones in your skin. Choose a shade of nude lipstick with similar undertones to your skin to complement your complexion best.
Try a hint of pink for fair skin. Go a bit darker if you have light olive skin. Try a golden beige for medium skin. Pick darker than you think for dark skin. Consider the tone of your skin when selecting a color.