关于JS判断正负给颜色的问题，如何解决？

<script>
    function countDown(maxtime, fn) {
        var timer = setInterval(function () {
            if (maxtime > 0) {
                var minutes = Math.floor((maxtime % 3600) / 60),
                    seconds = Math.floor(maxtime % 60),
                    msg = minutes + "分" + seconds + "秒";
                fn(msg);
                --maxtime;
            }
            else if (maxtime <= 0) {
                var minutes = Math.floor((maxtime % 3600) / 60),
                    seconds = Math.floor(maxtime % 60),
                    msg = minutes + "分" + seconds + "秒";
                fn(msg);
                --maxtime;
            }
        }, 1000);
    }

    var Time = [5, 121, 516, 156, 891, 198, 813, 511, 259, 516, 125, 813, 951, 489, 159, 223];
    for (var i = 0; i < 16; i++) {
        (function (i) {
            var obj = 'timer' + i;
            countDown
                (Time[i], function (msg) {
                    document.getElementById(obj).innerHTML = msg;
                    document.getElementById(obj).style.cssText = "color:green;color:red;"
                })
        })(i)
    }

script>

问一下怎么让字体颜色根据正负数显示绿红

你这里面也没有负数啊