Hi @Chris_Putnam and all,
Color selection is available in PIX4Dsurvey since last June. See the last answers from Nate in the post Selecting points within the point cloud by color would be great. - #26 by Nate_Moore.
PIX4Dsurvey lets you refine the classes that you make in PIX4Dmapper, create a grid of points (or smart points) from the terrain class, and then use them to make a TIN that can be exported to LandXML for your CAD, if this is your end goal. You can find a related conversation at Import Point Classification from Survey into Mapper.