Value Basics

Dark areas advance, or stand out, while light areas recede, or hang back. Dark areas also have more weight in terms of balance.
High contrast between light and dark looks dramatic, while more similar shades of gray produces a calm effect.
To emphasize a light element, place it against dark, to emphasize a dark element, place it on a light background.
If you squint, your eyelashes screen out the most obvious color differences. Contrast is reduced and you you'll see what stand out the most. Columns of type will appear gray.

Color Basics

Warm colors — the reds, yellows and oranges — advance, or come forward, while cool colors — blues and variations — recede back. Simple Example
Complimentary colors are opposites on the color wheel. These combinations tend to vibrate if placed against each other. Beware of using purple/orange, red/green, or blue/yellow in combination.
Use only for extreme attention-getting devices.

Choosing Colors for Layout

If you are not experienced in working with color, keep color schemes conservative, conventional, and simple. Use subtle shades of natural colors.
Subtle colors found in nature also make the best choices for most background or minor elements, especially if type appears on the color.
Avoid bold, highly saturated primary colors except in areas of maximum emphasis, and even then, use caution.
Choose colors from an analagous palette, or colors that reside on the same quadrant of the color wheel.
Type must always contrast sharply with background colors to be readable. Squint!