<input id="decompose" class="decompose" type="checkbox" checked>
<label for="decompose"> decompose (r+g+b)</label>
<div class="result">   
  <div>rgb(<span class="value-r">255</span> <span class="value-g">255</span> <span class="value-b">255</span>)</div>
  <div>#<span class="value-rhex">ff</span> <span class="value-ghex">ff</span> <span class="value-bhex">ff</span></div></div>
<div class="colors">
  <span id="red" class="r color"></span>
  <span id="green" class="g color"></span>
  <span id="blue" class="b color"></span>
</div>
<div class="panel">
  <label class="label-r">
    <span>decimal: <span id="value-r" class="value value-r">255</span></span>         
    <span>hex: <span id="value-rhex" class="value value-rhex">ff</span></span>
    <span><span id="value-rhex-16" class="i16">15</span> * 16 + <span id="value-rhex-1" class="i1">15</span></span>
    <input id="r" data-target="r" type="range" step="1" min="0" max="255" value="255">
  </label>
  <label class="label-g">
    <span>decimal: <span id="value-g" class="value value-g">255</span></span>         
    <span>hex: <span id="value-ghex" class="value value-ghex">ff</span> </span>
    <span><span id="value-ghex-16" class="i16">15</span> * 16 + <span id="value-ghex-1" class="i1">15</span></span>
    <input id="g" data-target="g" type="range" step="1" min="0" max="255" value="255">
  </label>
  <label class="label-b">
    <span>decimal: <span id="value-b" class="value value-b">255</span></span>         
    <span>hex: <span id="value-bhex" class="value value-bhex">ff</span></span>
    <span><span id="value-bhex-16" class="i16">15</span> * 16 + <span id="value-bhex-1" class="i1">15</span></span>
    <input id="b" data-target="b" type="range" step="1" min="0" max="255" value="255">
  </label>
</div>

:root {
  --size: 45vw;
}
html {
  font-family: Source Code Pro, sans-serif;
  box-sizing: border-box;
}
* {
  box-sizing: inherit;
}
body {
  line-height: 1.5;
  height: 100vh;
  margin: 0;
  overflow: hidden;
  background: #000;
  color: whitesmoke;
  font-size: .875rem;
  padding: 1rem;
}
.colors {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100vh;
}

.color {
  position: absolute;
  width: var(--size);
  height: var(--size);
  left: 0;
  right:0;
  top: 0;
  bottom: 0;
  margin: auto;
  mix-blend-mode: screen;
  border-radius: 50%;
  transition: transform 1s, border-radius 1s, color .5s;
}
.r {
  background: #f00;
}
.g {
  background: #0f0;
}
.b {
  background: #00f; 
}
.panel {
  position: absolute;
  height: 100vh;
  width: 100%;
  top: 0;
  left: 0;
}
.panel label {  
  position: absolute;
  padding: 1vw;
}
label > span {
  display: block;
}
.label-r {
  color: white;
  background: red;
  top: 50%;
  left: 50%;
  transform: translateY(calc(-0.75 * var(--size))) translateX(calc(-0.75 * var(--size)));
}
.label-g {
  background: lime;
  color: black;
  top: 50%;
  right: 50%;
  transform: translateY(calc(-0.75 * var(--size))) translateX(calc(0.75 * var(--size)));
}
.label-b {color: white;
  background: blue;
  bottom: 50%;
  left: 50%;
  transform: translateY(calc(0.75 * var(--size))) translateX(calc(-0.475 * var(--size)));

}
.decompose:checked ~ .colors .r {
  transform: translate3d(-25%, -25%, 0);
  border-radius: 0 50% 50% 50%;
}
.decompose:checked ~ .colors .g {
  transform: translate3d(25%, -25%, 0);
  border-radius: 50% 0 50% 50%;
}
.decompose:checked ~ .colors .b {
  transform: translate3d(0, 25%, 0);
  border-radius: 50% 50% 50% 0;
}
input[type="checkbox"],
label[for=decompose] {
  position: relative;
  z-index: 1;
}
.result {
  font-size: 1rem;
  bottom: .5rem;
  left: 0.5rem;
  background: black;
  position: absolute;
  z-index: 1;
  padding: .5rem;
}
.result div {
  margin-bottom: .5rem;
}
.result div + div {
  padding-left: 3ch;
  margin: 0;
}
.result [class*=r] {
  background: red;
}
.i16 {
  display: inline-block;
  width: 2ch;
}
.result span {
  display: inline-block;
  width: 4ch;
  text-align: center;
}
.result [class*=g] {
  background: lime;
  color: black;
}
.result [class*=b] {
  background: blue;
}

@media screen and (min-width:50em) and (min-height:50em) {
  :root {
    --size: 35em;
  }
}
@media screen and (min-width:50em) and (max-height:50em) {
  :root {
    --size: 60vh;
  }
}

const sliders = document.querySelectorAll("input[type=range]");
const colorCircles = {
  r: document.getElementById("red"),
  g: document.getElementById("green"),
  b: document.getElementById("blue")
};
const colorValue = {
  r: document.querySelectorAll(".value-r"),
  g: document.querySelectorAll(".value-g"),
  b: document.querySelectorAll(".value-b")
};
const colorValueHex = {
  r: document.querySelectorAll(".value-rhex"),
  g: document.querySelectorAll(".value-ghex"),
  b: document.querySelectorAll(".value-bhex")
};
const colorValueHex16 = {
  r: document.getElementById("value-rhex-16"),
  g: document.getElementById("value-ghex-16"),
  b: document.getElementById("value-bhex-16")
};
const colorValueHex1 = {
  r: document.getElementById("value-rhex-1"),
  g: document.getElementById("value-ghex-1"),
  b: document.getElementById("value-bhex-1")
};
const updateColor = ( element ) => { 
  const id = element.attributes["data-target"].value;
  const v = element.value;
  colorCircles[id].style.backgroundColor = `rgb(${v*(id === 'r')} ${v*(id === 'g')} ${v*(id === 'b')})`;
  console.log(colorValue[id]);
  colorValue[id].forEach( (el) => {
    el.innerHTML = v;
  });
  const hexString = parseInt(v).toString(16);
  colorValueHex[id].forEach((el) => {
    el.innerHTML = hexString.length === 1 ? '0'+hexString : hexString;
  });
  colorValueHex16[id].innerHTML = parseInt(v/16);
  colorValueHex1[id].innerHTML = parseInt(v%16)
}
sliders.forEach( element => {
  element.addEventListener( 'input', () => {
    updateColor( element ); 
  });
});