Again, this is such a simple Color Harmony that can so easily go wrong if you don't understand how color really works . So, here's the basics. Selecting a Complementary Color scheme starts, as most do, with a Color Wheel (see below). Start with one color and look directly across the wheel to find the color which is opposite from it and "Voila!" You have your Complementary Colors. Now, if you look around you've probably seen together before. Think about it, right around the Holiday season. Red and Green are directly across from each other on the color wheel. Historically "Purple and Gold" have been used to depict Royalty. Slide slightly over a little more on the wheel and you have "Plum and Sage"... and so on.
Easy right? Ok, now here's were many people go wrong. Most people only look for those "Two Colors" however, they don't consider the multiple tints and tones they could use to create a more polished or professional look. They simply pick the two colors and use them (the exact colors) together throughout the design. Unfortunately, if not done just right the result is a very flat feel.
Unless the design specifically requires a stark, crisp contrast consider using a slight variation of the colors in lighter and darker shades. This will add more visual interest to designs. Let's look at this great example. Look at the tablescape below. It's the old standard of "Red and Green" however, the "Red" takes the form of a tint of "Pink". Also, take a look at the subtle variation in the shades of Green in the Chair cover and the table overlays.
Did you also notice the different tints of pink in the overlay flowers and place setting too? Notice how the layering of colors adds a richer, more lush feel? Remember, it's the same colors just a little darker and lighter. Hope you enjoyed this portion of Behind the Design/Design 101... more Color Harmonies to come.