Sometimes it is the tiny little bit you don't even think of after having tried out thousands of things. Thank you matgg

 

A reinstall if the DX10 shaders patch (after having removed the C:\Users\[user]\AppData\Local\Microsoft\FSX\Shaders10 directory and files) helped me.

As mentioned earlier re aerosoft Madeira scenery and white runways I get the white runway at both airports during the day as well as night but all the taxiways are fine!