You can add your own paragraph styles, rename existing styles and delete styles you don’t want to keep. When you add, rename or delete a style, it affects the current presentation only, not all presentations you create using Keynote.
Note: You can’t add, rename or delete a paragraph style in a presentation shared with others.
To add a new style, you first modify the text of a paragraph in your presentation to look the way you want, then create the new style based on that text.
Go to the Keynote app on your Mac.
Open a presentation, select the text you want to modify, then make your formatting changes.
When you’ve finished, click anywhere in the modified text.
In the Format 
sidebar, click the Text tab.
Click the paragraph style name at the top of the sidebar, then click 
at the top of the Paragraph Styles menu.
A new style with a placeholder name appears in the menu.
Type a name for the new style, then click outside the menu to close it.
Go to the Keynote app on your Mac.
Open a presentation, then click any text.
In the Format sidebar, click the Text tab, then click the paragraph style name at the top of the sidebar.
In the Paragraph Styles menu, move the pointer over the style name you want to change, then click the arrow that appears.
Choose Rename Style, then enter a new name.
You can delete a style from the Paragraph Styles list that isn’t being used in your presentation. You might want to do this to simplify the pop-up menu to include just the styles you use most.
Go to the Keynote app on your Mac.
Open a presentation, then click any text.
In the Format sidebar, click the Text tab, then click the paragraph style name at the top of the sidebar.
In the Paragraph Styles menu, move the pointer over the name of the style you want to delete, then click the arrow that appears.
Choose Delete Style.
If you try to delete a style that’s being used, you’re asked to choose a style to replace the one you’re deleting.