Making a roof(unit) transparent for owner of entering unit only

I know that there has been several topics about this already, but all of them are so old that the attached sample maps are lost. This is why I would need help.

First: I want to use VertexColouring, not Hide/Show.
I read that I need to use GetLocalPlayer() with CustomScript.
But how? As I said, a sample map would be most appreciated! :)

This is how far ive gotten:

Unit enters region.

Set vertex colouring of roof to 85% Transparency.

(its not far, i know)

Event:
Unit enters region

Actions:
Custom Script: if GetLocalPlayer() == GetOwningPlayer(GetEnteringUnit()) then
Set vertex colouring of roof to 85% Transparancy
Custom Script: endif


Be very careful with what you put inside that GetLocalPlayer() - Block. Almost everything causes desyncs when executed in such a block. There are only a few exceptions. (like this one... hopefully)