AMezera,
You will have to insert the watermark on your master slide. Go to View - Master - make a textbox with the word draft - format it the way you want. You're all set, the watermark will be present on al the slides. WIth the watermark selected go to the contextual drawing tab, in the WordArt styles group click the Text fill button, apply a light grey theme colour, once applied you can play with it applying a colour transition using the same button.
Luc Sanders
MVP - PPT