Symptom
After opening a theme, making changes, and saving as a new theme, the changes do not appear to be saved. The new theme still contains the previous theme's settings.
Solution
Keynote themes are based on master slides, which contain the background and layout elements used in all new slides created with that theme.
If you open a new Keynote document using the gradient background theme, and change only the document's slide backgrounds and don't edit the master slides, the new theme you save will still have the gradient background.
To edit a master slide, you must be in the master slide organizer.
- Choose View > Show Master Slides to open the master slide organizer (or click View in the toolbar and choose Show Master Slides).