Bookmarklet to invert the colors of a website. One click inverts, second click removes the inversion. Paste as the URL inside a bookmark.

Doppelgänger.js

javascript:void function(){
  const d=document,q=d.querySelectorAll("style.dplgngr"),s=d.createElement("style");
  if(q?.length)return q.forEach(a=>a.remove());
  let b='#fff',i='95',h='180';
  s.type="text/css";
  s.className="dplgngr";
  s.innerText=`
    html { background-color: ${b}; }
    html,img,video,iframe { filter: invert(${i}%) hue-rotate(${h}deg); }
  `;
  d.body.appendChild(s);
}();

Doppelgänger.min.js

javascript:void function(){const b=document,c=b.querySelectorAll("style.dplgngr");if(c%3F.length)return c.forEach(a=>a.remove());const d=b.createElement("style");d.type="text/css",d.className="dplgngr",d.innerText="html { background-color: %23fff; filter: invert(95%25) hue-rotate(180deg); }img,video,iframe { filter: invert(95%25) hue-rotate(180deg); }",b.body.appendChild(d)}();