The Gen 8.0 version of the appication window shows:
The Gen 8.6 version of the application window has some 3D effect and the background colour for drop-down objects is white instead of grey:
The Gen 8.0 application has an associated manifest file built by the Build Tool which refers to Microsoft Windows Common Controls version 6.
The Gen 8.6 application has no manifest file and is picking the default version 5 of Microsoft Windows Common Controls: https://docs.microsoft.com/en-us/windows/win32/controls/cookbook-overview
Release : 8.6
Component : CA Gen Run Time, GUI
Build Tool C Profile token OPT.APPMANIFEST can be used to create an application manifest file (<load module>.EXE.manifest) which refers to "Microsoft.Windows.Common-Controls" version="126.96.36.199": CA GEN 8.6 > Profile Token Descriptions
NOTE: The documentation for OPT.APPMANIFEST is out of date because the options are no longer EMBEDDED/EXTERNAL but now YES/NO. The default is NO.
The template file used to create the application manifest file is %GEN86%\Gen\version\comctl.manifest.
To create <load module>.EXE.manifest in directory model.ief\c EITHER copy file %GEN86%\Gen\version\comctl.manifest OR rebuild the load module with OPT.APPMANIFEST=YES .
The look and feel of the window then matches the Gen 8.0 version.