<svg xmlns="http://www.w3.org/2000/svg">
    <filter id="filter">
        <feTurbulence baseFrequency="0.2"/>
        <feColorMatrix values="0 0 0 9 -4
                               0 0 0 9 -4
                               0 0 0 9 -4
                               0 0 0 0 1"/>
    </filter>
    <rect width="100%" height="100%" filter="url(#filter)"/>
</svg>

/* Add the seed attribute and set it to a random integer in <feTurbulence> to create your own variant! */
/* Minified (223 bytes):
<svg xmlns="http://www.w3.org/2000/svg"><filter id="a"><feTurbulence baseFrequency=".2"/><feColorMatrix values="0 0 0 9 -4 0 0 0 9 -4 0 0 0 9 -4 0 0 0 0 1"/></filter><rect width="100%" height="100%" filter="url(#a)"/></svg>
*/

External CSS

  1. https://codepen.io/finnhvman/pen/ExgLjmg.css

External JavaScript

  1. https://codepen.io/finnhvman/pen/ExgLjmg.js