To change the Class Properties of Lidar Classes, open the Filter Lidar Data window and right-click on an existing classification. This is also available in the Lidar section of the Configuration dialog.
Set Class Name... will allow you to customize the Lidar Class names. (If you export to LAS/LAZ files, the custom names that you selected will also be stored in those formats as they support custom classification schemas.)
Choose the option to set Set Class Color... to change the colors when using Color Lidar by Classification
Set Class Group(s)... will open the Select Lidar Groups window.
Each Lidar Class can be added to a number of groups that are used for Lidar Automatic Extraction and Lidar statistics like Height Above Ground. These are configured by default to coordinate with the ASPRS classification definitions, but can be customized for other classification schemes.