These usually go together as well as monochromatics, especially when one color is dominant. Contrasting schemes are colors separated by three segments. This strategy is trickier because some combinations clash. One trick is to make the duller color dominant and use the brighter one sparingly for accent. This approach yields a lively result.
Complementary schemes use colors that are opposites on the color wheel.
Be careful because this strategy can backfire, leaving you with garish combinations that assault the eye. You can back it down by using one color as a dominant and the other as an accent. One thing to remember is that the printing process can only approximate the colors you select. Regardless of your printer's expertise, some variations will occur due to paper, humidity, inks, the press and other variable. But with a grasp of some underlying theories behind the effective use of color, you'll be better prepared to choose colors that advance your communication objectives.