Is it possible to change the characteristic (line or face color, line thickness…) of a viewport for the layers made on SketchUp?
You can make style settings for the scene in SketchUp so they show in the viewport in LayOut. You can set a line weight multiplier for all the edges in the viewport under the Style tab in the SketchUp inspector window in LayOut. That multiplier will apply to all edges in the viewport, though. Or you can explode the viewport in LayOut and ungroup the edges. Then you can treat them like other line entities and change their color, thickness etc. in the Shape Style inspector window.