There are a couple of things you can tweak to customize what your documentation looks like.
Doctor Jekyll leverages the eight color themes defined by Lanyon. You can update the theme color by updating _sass/_variables.scss:
/* Selected Theme */
$theme_color: $red;
By default, the navigation sidebar is shown above the $medium-bp
breakpoint (960px). Below that screen width, the navigation menu is hidden and the drawer icon appears to toggle the menu. You can change the breakpoint value in _variables.scss.