Whether you're looking to reduce redness, brighten dark under-eye circles, or counteract sallowness, there's a Sleek Makeup Lifeproof Colour Corrector (£8) for you (shown here in mint green, a shade that looks like slime but actually helps neutralise any redness in your skin). Using a damp makeup sponge, dab a thin layer of the colour corrector to the desired area before you apply your base. You'll probably find that you don't need to use as much foundation/concealer as usual.
Image Sources: Courtesy of Benefit Cosmetics and Courtesy of Algenist