Color evokes feelings! There are two general categories of colors • cool (blue and green) • warm (orange and red) Use cool for backgrounds because cool colors recede from us into the background and use warm colors for objects in the foreground, like text because warm colors move objects towards us. While not strictly color related, you want to consider the following advice: If presenting in a dark room, use a dark background with white text; but if presenting with lights on, use a white background with black text. You can learn more about colors at CreativePro.com which provides an introduction to color use for Website, but the information is good for presentations as well. If you are interested in learning more, I suggest you visit the Color Matters which even explains why school buses are yellow.