This extension adds a basic form to the CTUS page.
Shadows, and Shadows-based ReadyThemes, ship with the Contact extension included. The CSS is part of /themes/%STORE_ID%/THEME_NAME/extensions.css and the JavaScript is in /themes/%STORE_ID%/THEME_NAME/extensions/contact/contact.js and only linked to the CTUS page. If you want to make styling changes, it is recommended you add them to your /themes/%STORE_ID%/THEME_NAME/theme.css file. The HTML for this extension can be accessed by navigating to RradyThemes -> Content Sections -> contact_form; you can modify the form processor by navigating to User Interface -> Pages -> CTFM.
If you are using Shadows DE, you can modify the CSS in build/extensions/contact/ and update as part of your build process.