Uh - what are you using to create the charts?
Most software packages will let you set your colors once you've created the chart. At that point, it's a matter of deciding on a palette. On a pie chart, I prefer to have fairly different colors for each "slice", especially if there are going to be multiple small "slices". For example, it's really hard to tell the difference between some shades of purple and some shades of blue if they're really small. Or, failing that, make sure that your "similar" colors are separated from each other (like the blues in this chart).
For bar charts, you may be able to get away with a fairly close palette - variations on the same shades of blue, for instance will probably be fine since there is a clear visual separation between the columns:
You could, of course, make one bar a completely different color if you're trying to draw the audience's attention to a single talking point ("...and as you can see, it would be much cheaper to raise a zombie army than to have to pay legions of live soldiers wages and benefits...".
One other word of caution: be careful of using patterns on any of these; charts often depend on the human eye to be able to tell the difference between the edges of the various shapes, and a pattern can very easily interfere with this ability. If you're going to use a pattern on a chart make sure it's not distracting.
BTW, I used MS Excel to make these as a quick and dirty set of illustrations. You can double-click on the pieces of the chart to re-assign colors, etc. Clearly, the process is going to be different depending on what you're using to create the charts.