设置lineStyle.normal.color后visualMap无效

描述:当前是关于Echarts图表中的 折线图 示例。
 
            var data = [
    [
        "2017-01-04 13:11:00",
        82.3
    ],
    [
        "2017-01-04 13:11:30",
        81.2
    ],
    [
        "2017-01-04 13:12:00",
        83
    ],
    [
        "2017-01-04 13:12:30",
        84.1
    ],
    [
        "2017-01-04 13:13:00",
        87
    ],
    [
        "2017-01-04 13:13:30",
        85.2
    ],
    [
        "2017-01-04 13:14:00",
        84.2
    ],
    [
        "2017-01-04 13:14:30",
        79
    ],
    [
        "2017-01-04 13:15:00",
        79.1
    ],
    [
        "2017-01-04 13:15:30",
        82.6
    ],
    [
        "2017-01-04 13:16:00",
        82.6
    ],
    [
        "2017-01-04 13:16:30",
        83.6
    ],
    [
        "2017-01-04 13:17:00",
        82.7
    ],
    [
        "2017-01-04 13:17:30",
        85.3
    ],
    [
        "2017-01-04 13:18:00",
        88.2
    ],
    [
        "2017-01-04 13:18:30",
        83.4
    ],
    [
        "2017-01-04 13:19:00",
        81.6
    ],
    [
        "2017-01-04 13:19:30",
        82.6
    ],
    [
        "2017-01-04 13:20:00",
        82.9
    ]
];
option = {
    "title": {
        "text": ""
    },
    "tooltip": {
        "trigger": "axis"
    },
    "xAxis": [{
        "type": "time",
        "splitLine": {
            "show": false
        }
    }],
    "yAxis": [{
        "type": "value",
        "splitLine": {
            "show": false
        },
        "max": "dataMax",
        "min": "dataMin"
    }],
    "visualMap": [{
        "show": false,
        "pieces": [{
            "lte": 80.7,
            "color": "red"
        }, {
            "gt": 80.7,
            "lte": 82.1,
            "color": "yellow"
        }],
        "outOfRange": {
            "color": "blue"
        },
        "seriesIndex": 0
    }],
    "series": [{
        "type": "line",
        "name": "test",
        "symbolSize": 10,
        "silent": false,
        "clipOverflow": true,
        "lineStyle": {
            "normal": {
                "color":"blue",//去掉color就正常了
                "width": 1
            }
        },
        "data": data
    }]
}