<input type="range" min="0" max="100" step="1" value="20">

<input type="range" min="0" max="100" step="1" style="--c: lightblue;--l: 6px;--g:12px;">

<input type="range" min="0" max="100" step="1" value="70" style="--c: red;--l: 4px;">

input {
  --c: orange; /* active color */
  --g: 8px; /* the gap */
  --l: 5px; /* line thickness*/
  --s: 30px; /* thumb size*/
  
  width: 400px;
  height: var(--s); /* needed for Firefox*/
  --_c: color-mix(in srgb, var(--c), #000 var(--p,0%));
  -webkit-appearance :none;
  -moz-appearance :none;
  appearance :none;
  background: none;
  cursor: pointer;
  overflow: hidden;
}
input:focus-visible,
input:hover{
  --p: 25%;
}
input:active,
input:focus-visible{
  --_b: var(--s)
}
/* chromium */
input[type="range" i]::-webkit-slider-thumb{
  height: var(--s);
  aspect-ratio: 1;
  border-radius: 50%;
  box-shadow: 0 0 0 var(--_b,var(--l)) inset var(--_c);
  border-image: linear-gradient(90deg,var(--_c) 50%,#ababab 0) 0 1/calc(50% - var(--l)/2) 100vw/0 calc(100vw + var(--g));
  -webkit-appearance: none;
  appearance: none;
  transition: .3s;
}
/* Firefox */
input[type="range"]::-moz-range-thumb {
  height: var(--s);
  width: var(--s);
  background: none;
  border-radius: 50%;
  box-shadow: 0 0 0 var(--_b,var(--l)) inset var(--_c);
  border-image: linear-gradient(90deg,var(--_c) 50%,#ababab 0) 0 1/calc(50% - var(--l)/2) 100vw/0 calc(100vw + var(--g));
  -moz-appearance: none;
  appearance: none;
  transition: .3s;
}
@supports not (color: color-mix(in srgb,red,red)) {
  input {
    --_c: var(--c);
  }
}


/**/
body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  gap: 40px;
  place-content: center;
  background: repeating-linear-gradient(-45deg, #fff 0 20px, #f9f9f9 0 40px)
}