<header class="header">
  <div class="header__title">
    <h1>
      <code>grayscale()</code>
    </h1>
  </div>
  <div class="header__reference">
    <ul class="reference-list">
      <li><a class="reference-list__link" href="https://developer.mozilla.org/en-US/docs/Web/CSS/filter-function/grayscale">MDN reference</a></li>
      <li><a class="reference-list__link" href="https://caniuse.com/#feat=css-filters">caniuse Support</a></li>
    </ul>
  </div>
</header>

<main>
  <div class="example">
    <p>
      In this example, you can toggle the removal of a grayscale effect, bringing <a href="https://birthmoviesdeath.com/2013/09/16/true-movie-magic-how-the-wizard-of-oz-went-from-black-white-to-color">the magic of Technicolor</a> to the land of Oz: 
    </p>

    <button 
      aria-pressed="false"
      class="button"
      type="button">
      Toggle grayscale
    </button>
  
    <div class="example__demo example__demo--grayscale">
      <img 
        class="yellow-brick-road" 
        alt="Dorothy, The Cowardly Lion, The Tin Man, and Scarecrow walking down the Yellow Brick Road. The city of Oz is visible on the horizon." 
        src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/11907/emerald-city.jpg" />
    </div>

  </div>
</main>
// Demo
.js-remove-grayscale {
  filter: grayscale(0) !important; // Forces immutability
}

.yellow-brick-road {
  filter: grayscale(1);
  transition: filter var(--transition-duration-longer) ease-in-out;
}


// Pen Setup
.example__demo--grayscale {
  padding: 0.5rem;
}

.yellow-brick-road {
  display: block;
  height: auto;
  width: 100%;
}
View Compiled
const button = document.querySelector('button');

function toggleGrayscale() {
  var yellowBrickRoad = document.querySelector('.yellow-brick-road');
  console.log("HELP");
  yellowBrickRoad.classList.toggle('js-remove-grayscale');
}

button.addEventListener('click', toggleGrayscale);


button.addEventListener('click', event => {
  if (button.getAttribute('aria-pressed') === "false") {
    button.setAttribute('aria-pressed', 'true');
  }
  else {
    button.setAttribute('aria-pressed', 'false');
  }
});

External CSS

  1. https://codepen.io/ericwbailey/pen/vMXWgz

External JavaScript

This Pen doesn't use any external JavaScript resources.