You can manually create a custom Gantt chart from scratch using the native Chart menu of PowerPoint. In its Chart menu, you can find several types of standard charts including line, bar, area, pie ...

If you've created a pie chart in your PowerPoint presentation and now want to change its colors, you can do this quite easily using the program's "Format Shape" options.

You can easily draw in PowerPoint to mark and edit slideshows, or create your own designs, especially if you're using a touchscreen.