How do I change my font/colours/logo?

To change the system font, navigate to Admin > System > Configuration and expand the User interface section. A preset font can be chosen from the Font drop down and (from version 10) a custom font file (extension woff2, woff, ttf or otf) can be uploaded with the Custom font file option.

You can change more UI elements in Admin > System > Configuration > User interface too, including the header background and link colours, system logo and simple search background colours, user collection bar background and foreground colours. Use the colour selector or enter a custom RGB colour code.