Need a simple application which displays the current system colours.

I am trying to create a basic visual c++ windows desktop application which will retrieve the current system colours. 

Microsoft include some example code that uses GetSysColors and SetSysColors at https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-setsyscolors 

I have used this example to make a test application however I saw nothing being displayed or any changes.

Any information would be great!