can't select single bar in diagram Power Point

Hello,

I want to change the colour of a single bar in a diagram in PowerPoint but unfortunately i can only select all the bars at a time. When I want to select a single number in the diagram it's no problem, just with the bars it doesn't work. I used a diagram created in Excel and transferred it to PowerPoint. Is there any other solution to select one bar besides clicking on it?

Thanks for your help,

Anja