javascript color changer

function changeColor () {

    function colordiff(a, b) {
        a = rgb(a);
        b = rgb(b);
        if (!(a && b)) return 10E+100;
        var d = [];
        d[0] = a[0] - b[0];
        d[1] = a[1] - b[1];
        d[2] = a[2] - b[2];
        var rmean = (a[0] + b[0]) / 2;
        d = Math.sqrt((((512 + rmean) * d[0] * d[0]) >> 8) + 4 * d[1] * d[1] + (((767 - rmean) * d[2] * d[2]) >> 8));
        //d = Math.sqrt(3 * d[0] * d[0] + 4 * d[1] * d[1] + 2 * d[2] * d[2]);
        return d;
    }

    function rgb(i) {
        var m = i.match(/^#([0-9a-f]{6})$/i);
        if (m) {
            m = m[1];
            return [parseInt(m.substr(0, 2), 16),
            parseInt(m.substr(2, 2), 16), parseInt(m.substr(4, 2), 16)];
        }
        m = i.match(/^rgb\s*\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*\)$/i);
        if (m) return [parseInt(m[1], 10), parseInt(m[2], 10), parseInt(m[3], 10)];
        return null;
    }

    function transformHSV(I, H, S, V) {
        var VSU = V * S * Math.cos(H * Math.PI / 180);
        var VSW = V * S * Math.sin(H * Math.PI / 180);
        var ret = [];
        I = rgb(I);
        ret[0] = (0.299 * V + 0.701 * VSU + 0.168 * VSW) * I[0] + (0.587 * V - 0.587 * VSU + 0.330 * VSW) * I[1] + (0.114 * V - 0.114 * VSU - 0.497 * VSW) * I[2];
        ret[1] = (0.299 * V - 0.299 * VSU - 0.328 * VSW) * I[0] + (0.587 * V + 0.413 * VSU + 0.035 * VSW) * I[1] + (0.114 * V - 0.114 * VSU + 0.292 * VSW) * I[2];
        ret[2] = (0.299 * V - 0.3 * VSU + 1.25 * VSW) * I[0] + (0.587 * V - 0.588 * VSU - 1.05 * VSW) * I[1] + (0.114 * V + 0.886 * VSU - 0.203 * VSW) * I[2];
        return ret;
    }

    function rgb_s(i) {
        return "rgb(" + Math.ceil(i[0]) + ", " + Math.ceil(i[1]) + ", " + Math.ceil(i[2]) + ")";
    }

    var mindiff = 1500;
    var c = "#3b5998";
    var h = 80;
    var s = 1.5;
    var v = 0.8;
    ['div', 'a', 'span', 'button'].forEach(function (e) {
        var x = document.getElementsByTagName(e);
        for (var i = 0; i < x.length; i++) {
            if (colordiff(x[i].currentStyle.backgroundColor, c) < mindiff) x[i].style.backgroundColor = rgb_s(transformHSV(x[i].currentStyle.backgroundColor, h, s, v));
            if (colordiff(x[i].currentStyle.color, c) < mindiff) x[i].style.color = rgb_s(transformHSV(x[i].currentStyle.color, h, s, v));
            if (x[i].type == "submit" && colordiff(x[i].currentStyle.backgroundColor, c) < mindiff) x[i].style.backgroundImage = 'none';
        }
    });

}