Answers for "change color of scrollbar"

change scrollbar color

body::-webkit-scrollbar {
  width: 12px;               /* width of the entire scrollbar */
}

body::-webkit-scrollbar-track {
  background: orange;        /* color of the tracking area */
}

body::-webkit-scrollbar-thumb {
  background-color: blue;    /* color of the scroll thumb */
  border-radius: 20px;       /* roundness of the scroll thumb */
  border: 3px solid orange;  /* creates padding around scroll thumb */
}

change scrollbar color

.scrollable-element {
  scrollbar-color: red yellow; /* red is for the thumb and yellow is for the track */
}

on scroll change navbar color

$(document).ready(function(){
    $(window).scroll(function(){
        if($(window).scrollTop() > $(window).height()){
            $(".menu").css({"background-color":"transparent"});   
        }
        else{
            $(".menu").css({"background-color":"white"});
        }

    })
})