Yes, there is no difference between the test and live version in relation to CSS.
We’ve built Themes for this purpose. A theme is a CSS file with a limited set of properties, which allow you to tune the look and feel of the UI. Think fonts, borders, colors, and so on. The core chat UI layout still stays the same, but you can make it fit your site’s design seamlessly.
Click the link below for further information on how to choose your own layout.