jQuery が背景色を直接アニメーション化しないのはなぜですか?それを修正するにはどうすればよいですか?

(function (d) {
    d.each(["backgroundColor", "borderBottomColor", "borderLeftColor", "borderRightColor", "borderTopColor", "color", "outlineColor"], function (f, e) {
        d.fx.step[e] = function (g) {
            if (!g.colorInit) {
                g.start = c(g.elem, e);
                g.end = b(g.end);
                g.colorInit = true
            }
            g.elem.style[e] = "rgb(" + [Math.max(Math.min(parseInt((g.pos * (g.end[0] - g.start[0])) + g.start[0]), 255), 0), Math.max(Math.min(parseInt((g.pos * (g.end[1] - g.start[1])) + g.start[1]), 255), 0), Math.max(Math.min(parseInt((g.pos * (g.end[2] - g.start[2])) + g.start[2]), 255), 0)].join(",") + ")"
        }
    });

    function b(f) {
        var e;
        if (f && f.constructor == Array && f.length == 3) {
            return f
        }
        if (e = /rgb\(\s*([0-9]{1,3})\s*,\s*([0-9]{1,3})\s*,\s*([0-9]{1,3})\s*\)/.exec(f)) {
            return [parseInt(e[1]), parseInt(e[2]), parseInt(e[3])]
        }
        if (e = /rgb\(\s*([0-9]+(?:\.[0-9]+)?)\%\s*,\s*([0-9]+(?:\.[0-9]+)?)\%\s*,\s*([0-9]+(?:\.[0-9]+)?)\%\s*\)/.exec(f)) {
            return [parseFloat(e[1]) * 2.55, parseFloat(e[2]) * 2.55, parseFloat(e[3]) * 2.55]
        }
        if (e = /#([a-fA-F0-9]{2})([a-fA-F0-9]{2})([a-fA-F0-9]{2})/.exec(f)) {
            return [parseInt(e[1], 16), parseInt(e[2], 16), parseInt(e[3], 16)]
        }
        if (e = /#([a-fA-F0-9])([a-fA-F0-9])([a-fA-F0-9])/.exec(f)) {
            return [parseInt(e[1] + e[1], 16), parseInt(e[2] + e[2], 16), parseInt(e[3] + e[3], 16)]
        }
        if (e = /rgba\(0, 0, 0, 0\)/.exec(f)) {
            return a.transparent
        }
        return a[d.trim(f).toLowerCase()]
    }
    function c(g, e) {
        var f;
        do {
            f = d.css(g, e);
            if (f != "" && f != "transparent" || d.nodeName(g, "body")) {
                break
            }
            e = "backgroundColor"
        } while (g = g.parentNode);
        return b(f)
    }
    var a = {
        aqua: [0, 255, 255],
        azure: [240, 255, 255],
        beige: [245, 245, 220],
        black: [0, 0, 0],
        blue: [0, 0, 255],
        brown: [165, 42, 42],
        cyan: [0, 255, 255],
        darkblue: [0, 0, 139],
        darkcyan: [0, 139, 139],
        darkgrey: [169, 169, 169],
        darkgreen: [0, 100, 0],
        darkkhaki: [189, 183, 107],
        darkmagenta: [139, 0, 139],
        darkolivegreen: [85, 107, 47],
        darkorange: [255, 140, 0],
        darkorchid: [153, 50, 204],
        darkred: [139, 0, 0],
        darksalmon: [233, 150, 122],
        darkviolet: [148, 0, 211],
        fuchsia: [255, 0, 255],
        gold: [255, 215, 0],
        green: [0, 128, 0],
        indigo: [75, 0, 130],
        khaki: [240, 230, 140],
        lightblue: [173, 216, 230],
        lightcyan: [224, 255, 255],
        lightgreen: [144, 238, 144],
        lightgrey: [211, 211, 211],
        lightpink: [255, 182, 193],
        lightyellow: [255, 255, 224],
        lime: [0, 255, 0],
        magenta: [255, 0, 255],
        maroon: [128, 0, 0],
        navy: [0, 0, 128],
        olive: [128, 128, 0],
        orange: [255, 165, 0],
        pink: [255, 192, 203],
        purple: [128, 0, 128],
        violet: [128, 0, 128],
        red: [255, 0, 0],
        silver: [192, 192, 192],
        white: [255, 255, 255],
        yellow: [255, 255, 0],
        transparent: [255, 255, 255]
    }
})(jQuery);