How to Create a Custom Color Scheme in PowerPoint 2013
If you don’t like any of the choices, click the More Colors button.
Doing this brings up the Colors dialog box. As you can see, PowerPoint displays what looks like a tie-dyed version of Chinese checkers. (Note that this dialog box comes up with the Standard tab selected. If you used the Custom tab the last time you used this dialog box, the Custom tab will be selected instead.)
Click the color that you want and then click OK. After you click OK, you’re whisked back to the Create New Theme Colors dialog box.