背景色を定期的に変更する

function setBackgroundColor(index) {
    var blue1 = 'rgba(52, 152, 219, 0.8)';
    var blue2 = 'rgba(41, 128, 185, 0.8)';
    var dark1 = 'rgba(52, 73, 94, 0.8)';
    var dark2 = 'rgba(44, 62, 80, 0.8)';
    var gray1 = 'rgba(149, 165, 166, 0.8)';
    var gray2 = 'rgba(127, 140, 141, 0.8)';
    var white2 = 'rgba(189, 195, 199,1.0)';

    var colors = [blue1, blue2, dark1, dark2, gray1, gray2, white2];

    if (!index || index > (colors.length - 1)) {
        index = 0;
    }
    var color = colors[index];

    setTimeout(function() {
        $('html').animate({
            backgroundColor: color
        }, 500);

        setBackgroundColor(++index);

    }, 30000);
}

$(document).ready(function() {
    setBackgroundColor();
});