Related to the Neos Design System, see Design System for the Neos products
The current situation with dropdown, cause some loundness issues. The shadow is not enough to see the limit of the option list, and it’s hard to focus on the content of the dropdown. Also the UI does not really focus on the current selection. When a drop down is open, the user need to select an option or close the dropdown.
A proposal should be to add a colorful border around the dropdown, to define the area, and use this color as the background of the dropdown first element. The color is also use on hover/focus in the option list. (blue is just an example, but feel quiet nice with a shades of grey)
About general Visual Loundness, check this one UI Visual Loudness