javascript - DOM Manipulation and styling the background

I have a list that I want to give a metal/metallic background for each item in the list using DOM manipulation.

List using Bootstrap 4

 

   
Item 1
   
Item 2
   
Item 3
   
Item 4
 

This is my attempt to style the background of the class.

var backGroundMetallic = document.getElementsByClassName("list-group");
for(var i = 0; i < backGroundMetallic.length; i++) {
  backGroundMetallic[i].style.backgroundColor = '#7fffd4';
}

I'm only able to put use one CSS color. Is there a way to reference a CSS class so I can use more than one style in order to style the background for the list to achieve making it metal/metallic?