Your computer monitor is capable of showing millions of colors. Projecting the same image on a screen will not show the same subtle color variations you see on the computer monitor. Two shades of red that are close together on the color wheel will probably project as the same shade of red on the screen. If you use a dark background, white and yellow letters will be the easiest for your audience to read. Use red and green text for emphasis in the same way you would use bold in a printed text document.
