Apply liquid foundation all over your face with a makeup sponge. Using a sponge is nice, especially if you're not a makeup girl, because it gives you the most natural-looking coverage without making you look like a clown. Blend, blend, blend! Use a full-coverage foundation rather than a tinted moisturizer, which is more sheer.
Get yourself some concealer with a yellow tint. Concealer is a lot thicker than regular foundation and covers a lot better (raccoon eyes, anyone?), so it's ideal for bruise cover-up. A yellow tint also is ideal because the yellow tones actually neutralize the color purple. Just a little bit of color theory for ya.
Squeeze or dab some concealer onto your index finger. Gently, tap your finger over your skin to distribute the concealer around the center of the bruise, the darkest area.
Keep up the tap action. Lightly dabbing your concealer on with your finger will give you better coverage. Work the concealer all over the bruise, feathering it out around the edges of the bruise for the most natural look. Tap-a-tap-tap until the concealer is blended and your bruise is magically gone.
Sweep translucent setting powder over your face to set the makeup. Don't forget to pack your concealer with you if you plan on going out; last-minute bathroom touch-ups may occur!