How can I change the barcolors?

In version 3.5*: Select properties from the menu by clicking with right mouse button on the question, click the tab barcolors. You can set the bar colors for the answers.

In version 4.*: Select the template slide in the bottom of your screen. Click with the right mouse button on the diagram en choose the tab “colors”. Here you can select the colors for your bars and apply them to all slides. If you want to change the colors of only one diagram you can change the colors for each answer.