Echart自定义悬浮tooltip 设置字体颜色

option = {
    tooltip : {         // Option config. Can be overwrited by series or data
        trigger: 'axis',
        //show: true,   //default true
        showDelay: 0,
        hideDelay: 50,
        transitionDuration:0,
        backgroundColor : 'rgba(255,0,255,0.7)',
        borderColor : '#f50',
        borderRadius : 8,
        borderWidth: 2,
        padding: 10,    // [5, 10, 15, 20]
        position : function(p) {
            // 位置回调
            // console.log && console.log(p);
            return [p[0] + 10, p[1] - 10];
        },
        textStyle : {
            color: 'yellow',
            decoration: 'none',
            fontFamily: 'Verdana, sans-serif',
            fontSize: 150,
            fontStyle: 'italic',
            fontWeight: 'bold'
        },
        formatter: function (params,ticket,callback) {
            console.log(params)
            var res = 'Function formatter : <br/>' + params[0].name;
            for (var i = 0, l = params.length; i < l; i++) {
                res += '<br/>' + params[i].seriesName + ' : ' + params[i].value;
            }
            setTimeout(function (){
                // 仅为了模拟异步回调
                callback(ticket, res);
            }, 1000)
            return 'loading';
        }
        //formatter: "Template formatter: <br/>{b}<br/>{a}:{c}<br/>{a1}:{c1}"
    },
    toolbox: {
        show : true,
        feature : {
            mark : {show: true},
            dataView : {show: true, readOnly: false},
            magicType : {show: true, type: ['line', 'bar', 'stack', 'tiled']},
            restore : {show: true},
            saveAsImage : {show: true}
        }
    },
    calculable : true,
    xAxis : {
        data : ['周一','周二','周三','周四','周五','周六','周日']
    },
    yAxis : {
        type : 'value'
    },
    series : [
        {
            name:'坐标轴触发1',
            type:'bar',
            data:[
                {value:320, extra:'Hello~'},
                332, 301, 334, 390, 330, 320
            ]
        },
        {
            name:'坐标轴触发2',
            type:'bar',
            data:[862, 1018, 964, 1026, 1679, 1600, 157]
        },
        {
            name:'数据项触发1',
            type:'bar',
            tooltip : {             // Series config.
                trigger: 'item',
                backgroundColor: 'black',
                position : [0, 0],
                formatter: "Series formatter: <br/>{a}<br/>{b}:{c}"
            },
            stack: '数据项',
            data:[
                120, 132,
                {
                    value: 301,
                    itemStyle: {normal: {color: 'red'}},
                    tooltip : {     // Data config.
                        backgroundColor: 'blue',
                        formatter: "Data formatter: <br/>{a}<br/>{b}:{c}"
                    }
                },
                134, 90,
                {
                    value: 230,
                    tooltip: {show: false}
                },
                210
            ]
        },
        {
            name:'数据项触发2',
            type:'bar',
            tooltip : {
                show : false,
                trigger: 'item'
            },
            stack: '数据项',
            data:[150, 232, 201, 154, 190, 330, 410]
        }
    ]
};

参考网址:http://echarts.baidu.com/echarts2/doc/example/tooltip.html