Tagify dropdown select list background style

Problem/Motivation

I thought I am pretty good with CSS, but no.
I have been trying to change the tagify select item background from white to black, but no luck.
No matter what I do, the dropdown select list with options are always white with grey text.

How can I change the style of the form-select options background?

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes