Elements missing from U3D PDF and colors aren't correct in some areas.
The colors are turning out white because the level of ambient light in the scene is very high. The solar lighting cancels this out in MicroStation, but not in 3D PDF.Select Ambient in the Light Manager (Settings - Rendering - Light Manager) dialog and turn the Lux level down to around 30..Switch on "Enable double-sided rendering" under Edit->Preferences->3D & Multimedia in Acrobat, it will all show up. Microstation will handle this geometry properly in future versions of MicroStation so this won't be necessary.