http://jgthms.com theme switcher

bookmarklet.js

javascript:(function(){s=document.createElement('script');s.type='text/javascript';s.src='https://raw.github.com/gist/1926444/b8bfd192702e0fa021fb349ed1605747f0dad271/jgthms.com%20theme%20changer';document.body.appendChild(s);})();

index.js

/* HTML */
var themes = document.createElement('div')
  , lightTheme = document.createElement('a')
  , darkTheme = document.createElement('a')

themes.className = 'themes'

lightTheme.innerHTML = '☀'
lightTheme.href = '#'

darkTheme.innerHTML = '☾'
darkTheme.href = '#'


/* JavaScript */
var color = localStorage.getItem('color') || '#002B36'

document.documentElement.style.backgroundColor = color

color === '#002B36' ?
    lightTheme.className = 'active' :
    darkTheme.className = 'active'

var toggleTheme = function(e) {
    e.preventDefault()
    var sibling = this.previousElementSibling || this.nextElementSibling
    this.className = ''
    sibling.className = 'active'

    color = darkTheme.className ? '#FDF6E3' : '#002B36'
    document.documentElement.style.backgroundColor = color
    localStorage.setItem('color', color)
}

lightTheme.addEventListener('click', toggleTheme)
darkTheme.addEventListener('click', toggleTheme)

themes.appendChild(lightTheme)
themes.appendChild(darkTheme)
document.body.appendChild(themes)


/* CSS */
var head = document.querySelector('head')
  , style = document.createElement('style')

style.innerHTML = '.themes{position:absolute;top:10px;right:10px}.themes>a{display:none;font-size:28px;border-bottom-width:0}.themes>a:first-child{color:#fdf6e3}.themes>a:first-child:hover{color:#eee8d5}.themes>a:first-child+a{color:#002b36}.themes>a:first-child+a:hover{color:#073642}.themes>.active{display:block}'
head.appendChild(style)

T'es un malade.

(J'avais songé à un truc comme ça en plus)