How to change specific portfolio page's nav bar only

Site URL: https://www.shiqius.com/work/newsaction

I tried several times but dont know how. I believe the code as below can solve this problem,  but I cannot find the id of my specific portfolio page. I want to change my unactive nav items into white in black background. Can anybody help me?

#collection-idnumber {

.header-nav-item a {

  color: white

  }

}

Hi,

Edit Newsaction post >> Add a Code Block at bottom of page > Paste this code

<style>
  div.header-nav-item:not(.header-nav-item--active) a {
    color: white !important;
}
</style>