Unfortunately the drop box look on Windows varies between Windows versions and applications as Microsoft itself is somewhat inconsistent.
For example if you go to Word and select the settings
screen, the drop boxes there are different than the drop boxes in the file open dialog used by Word. Add to this drop boxes on web pages also look different when using either Microsoft Edge as opposed to Microsoft IE (see it yourself at https://www.w3schools.com/tags/tryit.asp?filename=tryhtml_select
Complicating this more is the fact we allow you to control the color
of the drop box, both the drop area and the list items along with the hover color for list when displayed.
Basically there is no "Standard" look for drop boxes as it varies between OS releases and products.