Can't control the style inside Dropdown Menu (Form) different choices

Hi, the ‘choices’ inside my dropdown menu button have always the same font and style. I tried all I can imagine but I can’t find out how to change the text style of these choices.

Does anyone have an idea of how to edit the choice’s style?

My guess is that it will need custom code but I don’t know how to code…

Thanks a lot in advance for your help.