<div class="block">
<div class="btn-radio">
  <label>М/#000;</label>
</div>
  </div>

<div class="block">
<div class="btn-radio">
  <label>V/#ADFF2F;</label>
</div>
   </div>

.color {
  width:10px;
  height:10px;
  display:inline-flex;
}

.btn-radio label {
  visibility: hidden;
      opacity: 0;
}
  
.block {
  width:200px;
  height:200px;
  border:1px solid red;
  display: flex;
  margin-bottom:20px;
  position:relative;
}

.block:hover .btn-radio label {
  visibility: visible;
      opacity: 1;
    left: 0;
    right: 0;
    z-index: 2;
}

const regex = /#[a-f\d]{3,6};?/gi;
const replacement = '<span class="color" style="background: $&;"></span>';
document.querySelectorAll(".btn-radio label").forEach(n => {
  n.innerHTML = n.innerText.replace(regex, replacement);
});