Concealer will cover imperfections and flaws ready for makeup to be applied. It's not for covering the whole face.
Tip: There is an easy way to choose the best color for concealer and foundation. Take three shades that are likely to go with your skin tone and apply side by side along the jawbone. Take the ring finger and smooth each one into the skin. The color that blends into your skin tone is the one to go with. Discard the others.