<div>
  <input type="radio" name="option" id="option1" value="option1">
  <label for="option1">Option 1</label>
</div>
<div>
  <input type="radio" name="option" id="option2" value="option2">
  <label for="option2">Option 2</label>
</div>
<div>
  <input type="radio" name="option" id="option3" value="option3">
  <label for="option3">Option 3</label>
</div>

input[type="radio"] {
  /* 设置背景颜色 */
  background-color: #ff0000;
  
  /* 或者使用自定义样式 */
  /* background-image: url('radio.png'); */
  /* background-size: 20px; */
  /* background-repeat: no-repeat; */
  /* background-position: center; */
}

document.getElementById("option1").checked = true;