Эффект светофора

let a = document.querySelector('.item');
 
const colorMenu = [
{name: 'blue', interval: 1000},
{name: '', interval: 1000},
{name: 'red', interval: 1000},
{name: '', interval: 1000}
];
 
let count = 0;
 
let go = setTimeout(function change() {
if (count === colorMenu.length) {
count = 0;
}
 
a.style.background = colorMenu[count].name;
go = setTimeout(change,colorMenu[count].interval );
count = count + 1;
 
},1000);

let a = document.querySelectorAll('.item');
const colorMenu = ['blue', 'red', 'blue', 'red'];
 
let count = 0;
setInterval(function() {
  count = count % colorMenu.length;
  for (let i=0; i<a.length; i++) a[i].style.background = '';
  a[count].style.background = colorMenu[count];
  count++;
}, 1000)

//независимо от количества цвета и элементов
let elems = document.querySelectorAll('.item'),
    colors = ['gold','gray', 'red', 'green', 'yellow', 'blue'],
    countCol = 0,
    countElem = 0;
 
const changeColor = () => {
 
    if(countCol === colors.length) countCol = 0;
    if(countElem === elems.length) countElem = 0;
    
    if(countElem > 0) elems[countElem - 1].style.backgroundColor = '';
    else elems[elems.length - 1].style.backgroundColor = '';
    
    elems[countElem].style.backgroundColor = colors[countCol];
    
    countCol++, countElem++;
};
 
setInterval(changeColor, 1000);