What is a Favicon?

It is a small website/tab icon which can be found in your browser tab when visiting a page. See examples below of some popular favicons.

I do not know the hex code for the colour I want.

You can either google hex code for the colour Black or Blue or if there is a specific colour you had in mind you can download a chrome extension called ColorZilla which allows you to select a colour on a website or image and it will give you the hex code.

What type of files can I upload for the Logo, Favicon and Banner image?

JPG, JPEG, PNG, GIF, WEBP

Go to Settings > Branding > Preview in new tab > you should see it in your browser URL. It should look like this https://tracking.tryhutch.co.uk/my-store but instead of my-store it would be your brand name.