The eyedropper tool comes in handy when assigning the proper color to match your skytop. In the help file it says to hold the shift key and left click the color box. This is not accurate, it is Hold the shift key + left click + then right click
In order to get the right shading, you must select the !World sector, (Keyboard shortcut is the home key),...then in the editor panel select "properties." This will bring up sector ambient light, sector direction light, and sector fog.
Each one of these has a color box next to it, it is here where you get the eyedropper tool working. Put your mouse arrow over the box, then hold shift + right click + then left click. Your arrow changes to the eyedropper tool.
Now, in your scene window, go to a cloud/or color in the sky, left click on it to get the correct color shading for your scene. Once you get it to your liking, WRITE DOWN the number settings before you mess with it anymore,...it is very difficult to go back to what you had before...