Bill;
go to
www.colorbrewer.org. The only set of 4 colours that I've found that works for colour, black & white, projector viewing and colour deficient people is the 4--class sequential OrRd. If you only need three, there's a lot more choice. If you are using stacked bars, I would not use more than 3. If there are more than 3 categories, find another way to tell the story. Readability suffers when there's more than 3 levels.