JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.3/js/bootstrap.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-slider/10.2.0/bootstrap-slider.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-slider/10.2.0/css/bootstrap-slider.css">
<input id="ex1" data-slider-id='ex1Slider' type="text" data-slider-min="0" data-slider-max="100" data-slider-step="1" data-slider-value="50" />

<br />
<button class="colors" id="Yellow" hexa="#ffff00">Yellow</button>
<button class="colors" id="Magenta" hexa="#D9017A">Magenta</button>
<button class="colors" id="Cyan" hexa="#009FDF">Cyan</button>
<button class="colors" id="Black" hexa="#2D2926">Black</button>

CSS

#ex1Slider .slider-selection {
  background: #BABABA;
}

#Yellow {
  background-color: #FEDD00;
  border: none;
  color: black;
  padding: 20px;
  text-align: center;
  text-decoration: none;
  display: inline-block;
  font-size: 16px;
  margin: 4px 2px;
  border-radius: 12px;
}

#Magenta {
  background-color: #D9017A;
  border: none;
  color: white;
  padding: 20px;
  text-align: center;
  text-decoration: none;
  display: inline-block;
  font-size: 16px;
  margin: 4px 2px;
  border-radius: 12px;
}

#Cyan {
  background-color: #009FDF;
  border: none;
  color: white;
  padding: 20px;
  text-align: center;
  text-decoration: none;
  display: inline-block;
  font-size: 16px;
  margin: 4px 2px;
  border-radius: 12px;
}

#Black {
  background-color: #2D2926;
  border: none;
  color: white;
  padding: 20px;
  text-align: center;
  text-decoration: none;
  display: inline-block;
  font-size: 16px;
  margin: 4px 2px;
  border-radius: 12px;
}

#Orange021 {
  background-color: #FE5000;
  border: none;
  color: white;
  padding: 20px;
  text-align: center;
  text-decoration: none;
  display: inline-block;
  font-size: 16px;
  margin: 4px 2px;
  border-radius: 12px;
}

JavaScript

var slider = new Slider('#ex1', {
  formatter: function(value) {
    return 'Current value: ' + value;
  }
});

var colorPercentages = {};

var colors = document.getElementsByClassName("colors");

for (let i = 0; i < colors.length; i++) {

  if (!(colors[i].getAttribute("id") in colorPercentages)) {
    colorPercentages[colors[i].getAttribute("id")] = 0;
  }

  colors[i].addEventListener("click", function() {

    colorPercentages[colors[i].getAttribute("id")] = $("#ex1").val();
    colors[i].innerHTML = colors[i].getAttribute("id") + " " + $("#ex1").val() + "%";

    console.log(colorPercentages)
    //formula here!!
    let r = 255 * (1 - colorPercentages.Cyan / 100) * (1 - colorPercentages.Black / 100);
    let g = 255 * (1 - colorPercentages.Magenta / 100) * (1 - colorPercentages.Black / 100);
    let b = 255 * (1 - colorPercentages.Yellow / 100) * (1 - colorPercentages.Black / 100);

    $("body").css('background-color', 'rgb(' + r + ', ' + g + ', ' + b + ')');




  });
}