Using Composant with color

Hi everybody,
I’m new user of Sketchup and I have a little problem with the composant I’m using on my plan.
I can’t apply a color to the component (in red on my attachment).
They always appear transparent on the part texture.
I’ve tried modifying the component and using the “colorize” tool, but it doesn’t work.
Could you help me understand what I’m doing wrong?
I suppose this is a very silly question, but I’m stuck on this problem.

Try to upload the model in order to be helped

plan_sketchup.skp (1.0 MB)

Your components have materials applied inside so they don’t show the new material but the material inside them.
Also you have textures applied to back faces.
You should start by the essentials of SketchUp in https://learn.sketchup.com/

See: