What are theme styles?
Also known as a "preset", themes come with different styles which contain pre-configured settings for fonts, colors and layouts. These different looks are called theme styles. These theme style show the stylistic range of the theme and allow you to find the best look to build your store from. All presets have access to the same features and can be customized in the theme settings. Changing presets will not adjust any section content or settings.
To change the theme style, go to the Theme editor (Customize) and navigate to the Theme settings tab then click the Theme Style tab.