Change hover colour on a specific page

Hi,

I want to change my hover underline colour on a specific page to black, is there someone who can help me out? I want to change the colour on my About page to black

My website: etrenoir.net

I'm currently using this code for my hover underline:

header nav a:hover:after{
  transform: scaleX(1);
  }
  
header nav a:after {
  display:block;
  content: '';
  border-bottom: solid 1.5px #FFFFFF;  
  transform: scaleX(0);  
  transition: transform 250ms ease-in-out;
  z-index: 999;
  transform-origin :100% 50%;
 }
}

add to Page Header

<style>
  header nav a:after {
  border-color: black;
 }
</style>