Answers for "how to change css on scroll"

scrollbar change css

body::-webkit-scrollbar {
  width: 1em;
}
 
body::-webkit-scrollbar-track {
  box-shadow: inset 0 0 6px rgba(0, 0, 0, 0.3);
}
 
body::-webkit-scrollbar-thumb {
  background-color: darkgrey;
  outline: 1px solid slategrey;
}

css change overflow scrollbar

::-webkit-scrollbar {
    width: 12px;
}

/* Track */
::-webkit-scrollbar-track {
    -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.3); 
    -webkit-border-radius: 10px;
    border-radius: 10px;
}

/* Handle */
::-webkit-scrollbar-thumb {
    -webkit-border-radius: 10px;
    border-radius: 10px;
    background: rgba(255,0,0,0.8); 
    -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.5); 
}
::-webkit-scrollbar-thumb:window-inactive {
    background: rgba(255,0,0,0.4); 
}