F.lux for the web

dusk.js

// requires jQuery

function Color(r,g,b,a) {
    this.r = parseInt(r);
    this.g = parseInt(g);
    this.b = parseInt(b);
    this.a = parseFloat(a);
}

Color.prototype.rgb = function() {
    var a = isNaN(this.a) ? "" : ","+this.a;
    return "rgb(" + this.r + "," + this.g + "," + this.b + a + ")";
}

Color.prototype.normalize = function() {
    this.r = Math.round(this.r);
    this.g = Math.round(this.g);
    this.b = Math.round(this.b);
}

function duskify(elems) {
    for (var i = elems.length; i--;) {
        var elem = $(elems[i]);
        var channels = elem.css('background-color').match(/\d+/g);

        if (channels.length === 3)
            var rgb = new Color(channels[0], channels[1], channels[2]);
        else
            var rgb = new Color(channels[0], channels[1], channels[2], channels[3]);
        rgb.g /= 1.15;
        rgb.b /= 1.15;
        rgb.normalize();
        elem.css('background-color', rgb.rgb());
    }
}

$(document).ready(function(){

    var body = document.getElementsByTagName('body'); // get the body element itself
    duskify(body);
    var body_elems = document.body.getElementsByTagName('*'); // get every item under body
    duskify(body_elems);

});