Making bruises with makeup is one of the easiest special effects makeup tricks out there. A basic knowledge of what bruises looks like and some theater makeup is all you need to start scaring your friends and family. Add some fake blood for some extra spice and you'll be the friend every one is calling next Halloween. Once you learn how to make realistic bruises you can apply this knowledge as base for zombies and other characters.
Go to your local costume or theater supply shop and buy a "bruise wheel." There are a couple of makeup companies that make a bruise wheel, but Ben Nye is one of the more common brands that a lot of makeup artists use to create bruises and burns.
Start by applying the yellow tone first, smooth it out with your fingers. Don't worry about it being perfect--bruises are never perfectly round or perfectly one color.
Next blend the light green on top of the yellow using your fingers again. Leave the outer edges yellow.
Blend the red with your fingers, and mix it together with the green and yellow in the center then spread it outwards. Be sure to still leave the outer edges of the "bruise" yellow.
Create your points of impact. Take the dark blue and with your finger smudge it in the center. The dark color you don't want to blend so much as just lay on top of the other colors. Take your your time to just dab where you feel necessary, until it looks like a bruise. By not blending the darker color as much you will get more 3D effect. Feel free to lay the darkest color on a little heavier than the other colors.