在里面添加:header-cell-style="{ color: 'black' }"

 <el-table
    :data="tableData"
    style="width: 100%"
    height="250"
   :header-cell-style="{ color: 'black' }"
></el-table>

正确代码是

<template><el-table:data="tableData"style="width: 100%"height="250":header-cell-style="{ color: 'black' }"
><el-table-columnfixedprop="date"label="日期"width="150"></el-table-column><el-table-columnprop="name"label="姓名"width="120"></el-table-column><el-table-columnprop="province"label="省份"width="120"></el-table-column><el-table-columnprop="city"label="市区"width="120"></el-table-column><el-table-columnprop="address"label="地址"width="300"></el-table-column><el-table-columnprop="zip"label="邮编"width="120"></el-table-column></el-table>
</template><script>export default {data() {return {tableData: [{date: '2016-05-03',name: '王小虎',province: '上海',city: '普陀区',address: '上海市普陀区金沙江路 1518 弄',zip: 200333}, {date: '2016-05-02',name: '王小虎',province: '上海',city: '普陀区',address: '上海市普陀区金沙江路 1518 弄',zip: 200333}, {date: '2016-05-04',name: '王小虎',province: '上海',city: '普陀区',address: '上海市普陀区金沙江路 1518 弄',zip: 200333}, {date: '2016-05-01',name: '王小虎',province: '上海',city: '普陀区',address: '上海市普陀区金沙江路 1518 弄',zip: 200333}, {date: '2016-05-08',name: '王小虎',province: '上海',city: '普陀区',address: '上海市普陀区金沙江路 1518 弄',zip: 200333}, {date: '2016-05-06',name: '王小虎',province: '上海',city: '普陀区',address: '上海市普陀区金沙江路 1518 弄',zip: 200333}, {date: '2016-05-07',name: '王小虎',province: '上海',city: '普陀区',address: '上海市普陀区金沙江路 1518 弄',zip: 200333}]}}}
</script>