JSFiddle - React, Tailwind, and code Playground

HTML

<div class="overlay-info">
  <div class="popup">
    <div class="close-info">
      <span>&#x2716;</span>
    </div>

    <div class="popup-content">
      <p class="notice">
        ABCD
      </p>

      <div class="green-btn">
        <a href="#">Enter</a>
      </div>
    </div>
  </div>
</div>

CSS

body {
  -webkit-filter: grayscale(100%);
  filter: grayscale(100%);
}

.overlay-info {
  width: 100%;
  height: 100%;
  top: 0;
  position: fixed;
  background-color: rgba(0, 0, 0, 0.8);
  z-index: 19999;
}

.popup > * {
  -webkit-filter: grayscale(0) !important;
  filter: grayscale(0) !important;
}

.popup .close-info {
  width: 100%;
  height: 20px;
  padding-bottom: 30px;
}

.popup .close-info span {
  float: right;
  cursor: pointer;
}


.popup .popup-content {
  padding: 15px 0 15px 0;
}

.popup-content .green-btn a {
  width: 300px !important;
}

.green-btn {
  background: green;
  margin: 0 auto;
  padding: 0 5px;
  text-align: center;
  color: #fff;
  display: block;
  width: 160px;
  font-size: 14px;
  font-weight: normal;
  border-radius: 4px;
  line-height: 38px;
  border: 1px solid green;
}

.popup {
  background-color: white;
  position: relative;
  top: 20%;
  width: 550px;
  margin: 0 auto;
  border-radius: 5px;
  padding: 20px;
}