<div id="myDiv"></div>
<input type="radio" name="color" value="red">红色
<input type="radio" name="color" value="blue">蓝色
<input type="radio" name="color" value="green">绿色

var radios = document.getElementsByName("color");
for (var i = 0; i < radios.length; i++) {
  radios[i].addEventListener("change", changeColor);
}

function changeColor() {
  var selectedColor = document.querySelector('input[name="color"]:checked').value;
  var div = document.getElementById("myDiv");
  div.style.backgroundColor = selectedColor;
}