Color usage is an extremely important element in web design. Color can pull a design together and help guide the eyes to key elements on a web page. Color can also be used to effectively induce different emotional responses with your visitors. Proper color usage can help with usability and enhance the overall experience when used properly. Every great website will make effective use of color schemes and on the other side, nearly every bad design features ineffective color usage.
Color isn't only important for visual reasons, it often becomes a part of your overall business image due to the subconscious effects it has on individuals. For that reason, it's always important to consider the various meanings of colors on a cultural, emotional, and aesthetic level. When choosing a color scheme consider the following color meanings:
White: cleanliness, purity, neutrality
Black: darkness, elegance, emotional depth
Blue: serenity, sadness, peaceful, cleanliness, precision, appetite supressant
Gold: warmth, knowledge, wealth, prosperity, wisdom
Purple: Royalty, spirituality, mystery, wisdom
Brown: Earthiness, wholesome, stability, conventional
Green: nature, growth, freshness, money
Yellow: sunshine, enthusiasm, optimism, caution
Red: passion, anger, danger, high energy, power, determination, sex, stimulant
Orange: passion, enthusiasm, caution/danger, happiness, creativity, stimulant
Notice how some of the colors here have some contradictions? It's all in the context of how they are used with your message and the other colors that are combined with them. Also, keep in mind cultural differences when using color. For example, red in India is a color associated with weddings and marriage and white in many cultures is associated with death.
Things to Avoid
Always avoid excessive use of orange, yellow, and red. These colors are the most tiring for the eyes to view and may be off putting. Don't us a brightly colored flashing text to get a readers attention, it is annoying and will typically result in people clicking away rather than reading your content. Instead make nice use of contrasting color/background that is different from the main content, but still complements it. This doesn't mean one can't or shouldn't use red at all, but consider the context of your website.
Avoid boring color schemes. Overdoing a white background can quickly move from “crisp and clean” to very ordinary and boring. Add a bit of texture or ensure you use other colors that contrast and blend well.
Don't be afraid of color! Use a good color pallet should blend at least 3, but not usually more than 5 colors. Ensure you make good use of the color wheel! Use a blend of complementary and contrasting colors. Use websites like Kuler to help you test a variety of color combinations. You can create your own pallets and view and use other users pallets as well.