How to change the background color of an li through a button and to use the same button to return the li to its original color?

Question

everyone! I wrote the function below:

`function addClickEventToButton(buttonId, classReceiver) {
  let buttonChangeColors = document.getElementById(buttonId);
  let eventReceiver = document.getElementsByClassName(classReceiver);
  buttonChangeColors.addEventListener('click', function () {
    for (let i = 0; i < eventReceiver.length; i += 1) {
      if (eventReceiver[i].style.backgroundColor = 'rgb(238,238,238)') {
      eventReceiver[i].style.backgroundColor = 'white';
      } else {
        eventReceiver[i].style.backgroundColor = 'rgb(238,238,238)';
      }
    }
  });`

The objective is to change the background color of 3 li's to white whenever I click a button. This part worked. The next thing I want to do is, when I click the same button again, to return their background color to the original color. Can anyone tell me what I'm doing wrong and how to fix it?