Backgrounds that are neither very light nor very dark can work well for onscreen presentations. A very dark background is usually used with white or yellow text for contrast, but the result can be harsh. In a dark room, the white background can have the same effect. When you want to create a softer effect, use a mid-range green or blue. However, be sure the text contrasts sufficiently with the background for good legibility.
For legibility, you need to make sure that your background is on the light side and your text is very dark — dark blue or black. An easy way to check is to view the slide in grayscale, because then you aren’t influenced by your impressions of the color. To do this, choose the Color/Grayscale button on the Standard toolbar, next to the Zoom text box. Then choose Grayscale from the list that drops down. (In PowerPoint 2007, go to View tab> Color/Grayscale group> Grayscale. If your text is still clear, you’re OK.
* Try design variations
* Choose fonts and colors for legibility
* Copying colors from a Web site
* Choose colors based on desired results