A few simple colors used wisely will look much better. Use color to clarify, group things together, accent, or distinguish. Don't use color because you can. Keep the contrast high. It is sometimes a good idea to view your slides on a monochrome monitor to see if the contrast between foreground and background is high enough.
Some colors make better backgrounds than others.
Most people feel that dark backgrounds with light text are easier to read in a darkened room. Background colors like black, dark blue, dark burgundy, dark gray, and dark green are good choices. Text choices of white, yellow, and other light pastel colors work well. Be careful of using bright intense colors, they tend to vibrate and are also hard to read. Getting ready for your big talk Once your slides or overheads are finished and your talk is written, it is time to make sure you are ready.