Typically when I speak at events I get a deck that has a custom layout and color palette. If I am creating my own material I typically paste existing slides with diagrams I have constructed from past presentations or guidance which had completely different layouts and themes. This results in diagrams that typically have color issues or limited color palette to select from. Here is an example of one very simple diagram that had some animation to explain how you could take advantage of animation to create a better user experience.
Notice how the the options for Quick Styles has no variation in color and my drawing inherited very basic colors with the variations shown in the drop down. You can introduce more colors by selecting from a number of available themes buried in the Slide Master. To access these themes do the following:
Click on the View Tab, then select Slide Master.
Next, select the Colors dropdown.
From there you will get a list of Presentation theme palettes and Built-In palettes. Since I draw all of my diagrams/graphics using the Office theme, I can now select that and utilize the color variation in the Office theme to create consistent looking diagrams across different presentation templates and when these diagrams are pasted into the new presentations, they look the same.
Below is the diagram from above with the built-in office theme and the use of Quick Styles.
