Change color & fonts of all objects in a whole presentation

Hi experts,

I am facing a challenge. Maybe some of you know this and have a solution. I am a trainer and have created presentations for my training. When I do training for different vendors, they want the slides to all be in their corporate design.

That means for me to adapt hundrets of slides by hand to a new layout and new colors/fonts. How do you do that? Is there a solution e.g. to change the colors/fonts of all objects of a presentation over all slides easily? And ist there a solution to transform more or less automatic to a new master?

regards Bernd...