Use appropriate contrast and color schemes. Even the most advanced projection systems can be difficult to see at times. Strive for strong contrast between text and backgrounds. When in doubt use either black text on a light background or white text on a black background. Combinations such as red text on a blue background can often be very hard to read when projected in a large lecture hall.
Patterned backgrounds can also be very difficult.
Choosing an appropriate text color for a varying background can be a major challenge. If you are not sure, stick with a solid background color. Be prepared for technical difficulties. Even with extensive planning, computer-based slide show presentations often experience technical difficulties. If you have the time, it is always a good idea to have a backup copy of your presentation as color transparencies or handouts for your audience.