By watching How to Create a Custom Theme for Google Sites you will learn how you can apply develop custom color palettes for your site, select different fonts for different elements of your site, and how to add custom logos and images to your site's theme.
Applications for Education
Creating a custom theme for Google Sites could be a good way for students to express themselves a bit as they develop digital portfolios for your class. It could also be a good way to make your classroom website stand-out a bit from all of the other sites that use stock Google Sites designs.
Learn more about Google Sites in the following videos: