要使用javascript操作背景色属性，您需要：

//Set to red
document.getElementById("frame").style.backgroundColor="red"; 

//Save into variable
var color = document.getElementById("frame").style.backgroundColor;

var frameRef = document.getElementById("frameId");
//alternatively  you can get all farmes in one array
//var textRef = document.querySelectorAll(".frameClass");

function changeBg(newColor){
  frameRef.style.backgroundColor =  newColor;
}

<button type="button" onclick="changeBg('red')" value="red">Red</button>
<button type="button" onclick="changeBg('blue')" value="blue">Blue</button>