Use multiple slide masters in one presentation
If you use more than one theme in your presentation, you’ll have multiple slide masters. Each slide master represents each theme.
For example, in the image that follows, there are two slide masters (with associated layouts beneath each) as you would see them in Slide Master View. Each slide master has a different theme applied to it.
an additional slide master to a presentation
On the View tab, click Slide Master.
On the Slide Master tab, do one of the following:
In the Edit Theme group, click Themes, and then under Built-in, select a theme that you want the additional Slide Master to adhere to.
In the Edit Master group, click Insert Slide Master.
Note When you insert a Slide Master using the ‘b’ procedure, the slide master appears without theme color and effects.