Guest UI
In the guest UI, we provide the ability to customize the look and feel of the account's guest-facing interfaces, including guest ordering, kiosk and Advanced Customer Display.
Sites can customize many of the UI elements, such as colors, dimensions, fonts, margins, media and the text to better represent their brand on guest-facing interfaces.
PDF (from September 2018)
Although some information is out of date on this document, it's useful to see how the pages and individual UI elements are laid out. It also provides sizes, alignment and enum information.
Example:
