Is it a bug.........if i create a file, apply textures and colors,  them save it as "A", close Lumion, then open it, apply textures and colors to layers, then save this file as "B", of course, close Lumion, then open the"A" file and find that all the textures and colors belong to the "B" file.

Same thing if i modify my .dwg file in AutoCAD, then reload it in "A" file, it reload itself in the "B" file even if i didn't reload it.

Not practical at all..............

No, it's not a bug - this is how Lumion works.

The materials that you assign to an imported model are saved every time you use the Edit materials function, not when you save your scene.

In other words, imported models and scene files are separate entities in Lumion.

This is in sharp contrast to SketchUp, 3DS Max and other programs where everything (scene and models - including material assignments) are saved in the scene file.

If you need a copy of an imported model but with different materials you will have to copy+rename the up to 4 model files in Documents/Lumion 2/Library and restart Lumion for the copy to show up in the model browser.