<div>
        <h2 id=rangeValue></h2>
        <div id="fillRangeValue"></div>
        <input type="range" class="range" name="" value="0" min="0" max="100" onmousemove="rangeSlider(this.value)"
            onchange="rangeSlider(this.value)">
    </div>

* {
  margin: 0;
  padding: 0;
}
body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background-color: #151515;
}
div {
  position: relative;
}
/*  */
#rangeValue { /* Проценти */
  position: relative;
  display: block;
  font-size: 6em;
  color: rgba(0, , 0, 0.8);
  font-weight: 800;
  z-index: 2;
  text-align: center;
}
#rangeValue::after {
  content: "%";
}

#fillRangeValue { /* слайдер  */
  position: fixed;
  top: 0;
  width: 0;
  left: 0;
  height: 100%;
  background-color: #00adff; /* колір слайдера */
  z-index: 1;
}
.range {
  position: relative;
  width: 400px;
  height: 15px;

  background-color: rgba(0, 0, 0, 0.8);
  outline: none;
  border-radius: 15px;
  box-shadow: 0 0 0 2px #151515, inset 0 0 5px #000;
  z-index: 2;
  overflow: hidden;
}
.range::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 15px;
  height: 15px;
  border-radius: 50%;
  background-color: #00adff;
  border: 4px solid #222;
  z-index: 2;
  box-shadow: -407 0 0 400px #00adff;
}

function rangeSlider(value){
    document.getElementById('rangeValue').innerHTML = value;
    document.getElementById('fillRangeValue').style.width = +value+"%";
  background ='linear-gradient(to right, hsl(6, 100%, 80%), hsl(335, 100%, 65%) ' + value + '%, #fff ' + value + '%, white 100%)'
};