I have never read this anywhere but I’ll bet $3.19 that I’m not the first to discover it. I absolutely suck at picking colors for anything and presentations are no different. I used to just stick with safe black, white, and greys.

One successful technique I’ve used more recently though in putting together a color scheme for slides is:

1. Find a cool picture that you want to use in the presentation (hint: see iStockPhoto)
2. Use the eyedropper in Keynote to swipe key colors from the picture for background, fonts, etc
3. Rock out!

You end up with a cohesive feel to the whole presentation as the image ties together the key colors. Give it a shot!