JSFiddle - React, Tailwind, and code Playground

HTML

<form onsubmit="return mySubmitFunction(event)"> <!-- IMPORTANT TO ADD -->
  <label class="container">Label text here
    <input type="checkbox" id="cboxEffectiveness" name="effectiveness"> <!-- This is the checkbox, is hided -->
    <span id="cboxEffectivenessSpan" class="checkbox"></span> <!-- This span is the visible CSS checkbox -->
  </label>
  <input type="submit" value="Wirksamkeit"> <!-- Submit button -->
</form>

CSS

/* The container */
.container {
  display: block;
  position: relative;
  padding-left: 35px;
  margin-bottom: 12px;
  cursor: pointer;
  font-size: 22px;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}

/* Hide the browser's default checkbox */
.container input {
  position: absolute;
  opacity: 0;
  cursor: pointer;
  height: 0;
  width: 0;
}

.checkbox {
  position: absolute;
  top: 0;
  left: 0;
  height: 25px;
  width: 25px;
  background-color: gray;
}

.checkbox.NotCheckedOnSubmit {
  position: absolute;
  top: 0;
  left: 0;
  height: 25px;
  width: 25px;
  background-color: red;
}


/* When the checkbox is checked, add a blue background */
.container input:checked ~ .checkbox {
  background-color: #fff;
}

/* Create the checkmark/indicator (hidden when not checked) */
.checkbox:after {
  content: "";
  position: absolute;
  display: none;
}

/* Show the checkmark when checked */
.container input:checked ~ .checkbox:after {
  display: block;
}

/* Style the checkmark/indicator */
.container .checkbox:after {
  left: 9px;
  top: 5px;
  width: 5px;
  height: 10px;
  border: solid black;
  border-width: 0 3px 3px 0;
  -webkit-transform: rotate(45deg);
  -ms-transform: rotate(45deg);
  transform: rotate(45deg);
}

JavaScript

function mySubmitFunction(e) {
  var cbox = document.getElementById('cboxEffectiveness');
  var span = document.getElementById('cboxEffectivenessSpan');
  if(cbox.checked == false){ // if the checkbox is not checked turn the span to red
  	span.classList.add('NotCheckedOnSubmit'); // adding the red class to the span
    return false; // not submitting
  }else{
  	alert('Submited!');
    return true;
  }
}