This article below provides detailed guidance on how to apply a pre-built color scheme in PowerPoint.
Step 1: Navigate to the Design -> Variants -> select one of the pre-built templates:

Step 2: If you want to choose different color schemes, click the arrow -> Colors -> a list of coordinated colors will be displayed -> choose a color suitable for your slide:

Step 3: If you want to add additional effects to the background color, click Effects -> choose suitable effects:

Step 4: To make the slide stand out more, click Background Style to select additional pre-built background color templates:

- The result after applying the pre-built templates:

Here is a detailed guide on how to apply a pre-built color scheme in PowerPoint.
Wishing you all success!
