might be best explain with an example: say I want to change the border to red instead of black after I made a selection.

here’s the link to sample code: https://www.w3schools.com/tags/tryit.asp?filename=tryhtml_select

on page load, the dropdown list has a “normal” border around it.

after I made a selection, the border-width seems to have doubled.

I thought the CSS might be a pseudo-class but looking at this list (https://developer.mozilla.org/en-US/docs/Web/CSS/Pseudo-classes), I cannot see anything that might be suitable.