In a black-and-white photo, the color palette is restricted to white, black and shades of gray. To create contrast, the photographer pits lighter elements against dark, sun against shadows. In color photography, the artist's palette is infinite and good contrast requires more consideration.
Good color contrast starts with the color wheel. On one side of the wheel are the "warm" colors: shades of yellow, orange, red and pink. On the other side are the "cool" colors: hues of violet, purple, blue and green. Choose the brightest shade of red and draw a line straight through the center of the wheel to the other side, landing on bright green.
Colors like red and green that live on opposite sides of the color wheel are called complementary colors -- think of Christmas decorations. They're simply pleasing to the eye. The same is true of other complementary pairs like yellow and purple, or orange and blue. Even if the colors don't sit exactly opposite each other on the wheel, the complementary effect is still there, like blue and red, or green and orange.
Keep these complementary color pairs in mind when you're composing a shot. A lush green forest is a remarkable image, but it's even more stunning with a splash of red or deep pink flowers. An aging orange-hued adobe wall is even more picturesque when contrasted with a cracked blue wooden door.
For the best color contrast, keep things simple [source: Tang]. The fewer colors in the image, the more dramatic and effective the contrast. The splash of red in your green forest scene can easily get lost in the noise of dozens of other bright colors. If you want to create a moody, subtle image, try to fill it with shades of color that are all huddled in one section of the color wheel.
Let's finish with some tips on getting great contrast in black-and-white photography.