To do Alt + H + T + C on Mac in PowerPoint, download and install Accelerator Keys, then press Option, followed by H, T, then C.
Command: Text Highlight Color
This is how to do Alt + H + T + C on Mac in PowerPoint with Accelerator Keys, the native ribbon and alt key shortcut solution for Mac users who get more done with PowerPoint.
Alt + H + T + C opens the Text Highlight Color menu, displaying a palette of highlight colors you can apply to selected text. Highlighting makes text stand out with a colored background, similar to using a highlighter marker.