js表格内边框颜色设置

<table style="border-collapse: collapse;">
  <tr>
    <td style="border: 1px solid red;">单元格1</td>
    <td style="border: 1px solid red;">单元格2</td>
  </tr>
  <tr>
    <td style="border: 1px solid red;">单元格3</td>
    <td style="border: 1px solid red;">单元格4</td>
  </tr>
</table>

<table id="myTable" border="1">
  <tr>
    <td>单元格1</td>
    <td>单元格2</td>
  </tr>
  <tr>
    <td>单元格3</td>
    <td>单元格4</td>
  </tr>
</table>

<script>
  var table = document.getElementById("myTable");
  table.style.borderCollapse = "collapse";
  var cells = table.getElementsByTagName("td");
  for (var i = 0; i < cells.length; i++) {
    cells[i].style.border = "1px solid blue";
  }
</script>

/* 在CSS文件或<style>标签中 */
.border-blue {
  border-collapse: collapse;
}
.border-blue td {
  border: 1px solid blue;
}

<table class="border-blue">
  <tr>
    <td>单元格1</td>
    <td>单元格2</td>
  </tr>
  <tr>
    <td>单元格3</td>
    <td>单元格4</td>
  </tr>
</table>