(function (tree) {
//
// RGB Colors - #ff0014, #eee
//
tree.Color = function (rgb, a) {
    //
    // The end goal here, is to parse the arguments
    // into an integer triplet, such as `128, 255, 0`
    //
    // This facilitates operations and conversions.
    //
    if (Array.isArray(rgb)) {
        this.rgb = rgb;
    } else if (rgb.length == 6) {
        this.rgb = rgb.match(/.{2}/g).map(function (c) {
            return parseInt(c, 16);
        });
    } else {
        this.rgb = rgb.split('').map(function (c) {
            return parseInt(c + c, 16);
        });
    }
    this.alpha = typeof(a) === 'number' ? a : 1;
};
tree.Color.prototype = {
    eval: function () { return this },

    //
    // If we have some transparency, the only way to represent it
    // is via `rgba`. Otherwise, we use the hex representation,
    // which has better compatibility with older browsers.
    // Values are capped between `0` and `255`, rounded and zero-padded.
    //
    toCSS: function () {
        if (this.alpha < 1.0) {
            return "rgba(" + this.rgb.map(function (c) {
                return Math.round(c);
            }).concat(this.alpha).join(', ') + ")";
        } else {
            return '#' + this.rgb.map(function (i) {
                i = Math.round(i);
                i = (i > 255 ? 255 : (i < 0 ? 0 : i)).toString(16);
                return i.length === 1 ? '0' + i : i;
            }).join('');
        }
    },

    //
    // Operations have to be done per-channel, if not,
    // channels will spill onto each other. Once we have
    // our result, in the form of an integer triplet,
    // we create a new Color node to hold the result.
    //
    operate: function (op, other) {
        var result = [];

        if (! (other instanceof tree.Color)) {
            other = other.toColor();
        }

        for (var c = 0; c < 3; c++) {
            result[c] = tree.operate(op, this.rgb[c], other.rgb[c]);
        }
        return new(tree.Color)(result, this.alpha + other.alpha);
    },

    toHSL: function () {
        var r = this.rgb[0] / 255,
            g = this.rgb[1] / 255,
            b = this.rgb[2] / 255,
            a = this.alpha;

        var max = Math.max(r, g, b), min = Math.min(r, g, b);
        var h, s, l = (max + min) / 2, d = max - min;

        if (max === min) {
            h = s = 0;
        } else {
            s = l > 0.5 ? d / (2 - max - min) : d / (max + min);

            switch (max) {
                case r: h = (g - b) / d + (g < b ? 6 : 0); break;
                case g: h = (b - r) / d + 2;               break;
                case b: h = (r - g) / d + 4;               break;
            }
            h /= 6;
        }
        return { h: h * 360, s: s, l: l, a: a };
    }
};


})(require('less/tree'));

@@ -449,24 +449,236 @@
         %7D);%0A
+    %7D else if (rgb.length == 8) %7B%0A        this.alpha = parseInt(rgb.substring(0,2), 16) / 255.0;%0A        this.rgb = rgb.substr(2).match(/.%7B2%7D/g).map(function (c) %7B%0A            return parseInt(c, 16);%0A        %7D);%0A
     %7D else %7B

Support for IE's ARGB syntax (#aarrggbb)