I'm using this free theme -

@media (min-width: 241px) and (max-width:768px)
{
   #s::placeholder 
   {
       color:000;
   }
}

if not work media query :

#s::placeholder 
 {
      color:000;
 }

CodePudding user response：

Somewhere the color white is set for the placeholder. Try to set the color you want as important.

I hope, I helped you

input#s::placeholder {
    color: black !important;
}