Many years ago, it was common advice among makeup and beauty experts to suggest that women wear concealers that are one shade lighter than their foundations. This advice circulated many years ago when it was not common for teenagers to wear makeup, and before adult acne became even more common.
According to beauty expert Paula Begoun, you should use a concealer under and around your eyes that is just a shade lighter than your foundation, but when choosing a concealer to cover acne and any other discolorations on your face, you should choose one that matches your foundation exactly.
The technique you use to apply concealer to hide blemishes is also very important, so check out this youtube video to see a great blemish coverage tutorial.
Using a concealer on acne that is a shade lighter than your face will not only call attention to the blemish, but also cause it to look larger. However, you want your makeup to draw attention to your eyes, and concealer around your eyes that is a bit lighter than your foundation will help them stand out and make you look more well-rested.