To access it you have to navigate to the Appearance / Customize/General.
Admin Panel → Appearance → Customize → General
Here you set the primary color for your website, in our example/demo you will see the primary color to be blue. If you click the color selector you can drag it around until you find a suiting color or enter a custom hex code/RGB color code.
To access it you have to navigate to the Appearance / Customize/ Site Identity.
Admin Panel → Appearance → Customize → Site Identity
This is where you set the logo for your website. It is displayed on the top of your header.