For blemishes and application over your foundation, go with a concealer that matches your foundation. If you plan to apply concealer under the eyes or to brighten certain areas, go for a shade slightly lighter and apply it over your foundation. For a concealer that you plan to wear without foundation, match it to your natural skin tone. Be sure to pay attention to warm and cool undertones to make sure your concealer isn’t too yellow or too pink for your skin tone.