JavaScript Brightness

/**
 * http://www.sitepoint.com/javascript-generate-lighter-darker-color/
 */

function colorLuminance(hex, lum) {
    // Validate hex string
    hex = String(hex).replace(/[^0-9a-f]/gi, "");
    if (hex.length < 6) {
        hex = hex.replace(/(.)/g, '$1$1');
    }
    lum = lum || 0;
    // Convert to decimal and change luminosity
    var rgb = '#', c;
    for (var i = 0; i < 3; ++i) {
        c = parseInt(hex.substr(i * 2, 2), 16);
        c = Math.round(Math.min(Math.max(0, c + (c * lum)), 255)).toString(16);
        rgb += ('00' + c).substr(c.length);
    }
    return rgb;
}

Penggunaan 

colorLuminance('#aabbaa', 0.5); // lighter
colorLuminance('#aabbaa', -0.5); // darker

Lihat Demo