Hi does anyone know how to change the default grey background colour where you click on a dropdown input menu and select an option?

It’s purely aesthetic, but Editor X does not seem to allow you to change the standard grey background colour of a dropdown input box - which looks a bit 1990s to me and clashes with the colour of my form!

I suspect I will need a snippet of code to do this, anyone able to help please? Unfortunately I am not familiar with code, but if some brainbox on here could tell me exactly where to copy and paste the relevant code and anything else that I would need to do - that would be amazing!