Colors and images on your web page can not only 'jazz up' its appearance, but also be used to convey important information. In fact, in many cases, such as experimental results, homework solutions, etc mechanical drawings or artistic images may be the purpose of sections of your web site.
However, it is important to use visual elements like color and images wisely. The way you lay out your pages, and your use of color, will affect not only people's perceptions of your page, but whether they can use it at all. (For instance, putting red text on a gray background may lose you color-blind users!)
Getting images on your web page.
In-depth Color information: RGB Color