Can I use a code to change the color of the language's text?

Hi there. I have been playing around and getting my website ready and I'm nearly there. Everything looks great and I have used some code I've seen to make it look nice.
Now my problem is that the language category on the header doesn't turn black when I scroll down so it disappears since the background of the header goes white. Any idea of how to fix this and have it turn black like the rest of the pages linked?
This is all the code I have on my site:

@font-face {
font-family: 'EB';
src: url(https://static1.squarespace.com/static/6568c0e50c68f524b12e50d4/t/6574fdba16df0b5b1ec4003f/1702165948139/EBGaramond-Italic-VariableFont_wght.ttf);
}h1 {
font-family: 'Pluto medium';
font-size: 40pt;
letter-spacing: 1px;
line-height: 140%;
}h1 {

  font-weight: 300 !important;

}h2 {
font-family: 'Pluto Medium';
font-size: 30pt;
letter-spacing: 1px;
line-height: 140%;
} 
@font-face {
font-family: 'Pluto Medium';
src: url(https://static1.squarespace.com/static/6568c0e50c68f524b12e50d4/t/65772fca005e376fbdb6813b/1702309834387/FontsFree-Net-Pluto-Medium.ttf);
}
#header {
  background-color: transparent;
}
.header-announcement-bar-wrapper {
  background-color: rgba(0,0,0,0)!important;
  -webkit-backdrop-filter: blur(0px);
  backdrop-filter: blur(0px);
}
.tweak-fixed-header .shrink.header {
  background: #ffffff !important;  
}
.tweak-fixed-header .shrink.header .header-nav-wrapper a {
  color: #000 !important;
}
div.header-menu-nav-folder .language-picker-content {
    background-color: black !important;
}

Thank you!

Hi,

What is site url? We can check your problem easier

www.coastlinejj.com