To change the page style for a button you have already created, you can modify the button's HTML code. Replace the value of the "page_style" variable with the Page Style Name of the style you wish to apply. The next time the button is clicked, its payment pages will appear in the new style. Specifying the "cs" and "image" variables in the button code will also override your Primary page style.
So if you have a single paypal account and multiple shopify stores, you would also find this useful. Please upload and comment +1 if this is a feature you would require.