How can I choose colors and fill patterns for individual bars in a bar graph?

Bars from a particular data set (column) always have the same color and fill pattern. To assign different colors to different bars, you must enter the data in different data sets.

If you have one group of bars, enter the data on one row, one value per column. That way, each bar is its own dataset, and you can assign a different color and fill pattern to each bar. (To rearrange your data, copy it to the clipboard, choose "Edit.. Paste special", then "Transpose" (Placement tab).

Also consider making a column bar graph. In this kind of graph, each bar plots the mean of all the values in a column. In Prism 4, choose the column bar graph in the 'one grouping variable' tab). You can assign to each bar in a column bar graph a different color and fill.

To get an in-depth grasp of one-variable bar graphs, consult one of these step-by-step examples for Prism 3 or Prism 4. For two-variable bar graphs, check these examples for Prism 3 and Prism 4.