vlad35,
как вариант...
<div style="width:300px; height:300px; background-color:red;" id="col"></div>
<script>
let color = ["green", "blue", "red", "orange"],
el = document.querySelector('#col'),
requests = color.reduce((promiseChain, item) => {
return promiseChain.then(() => new Promise(resolve => {
setTimeout(() => (el.style.background = item) && resolve(), 1000)
}));
}, Promise.resolve());
</script>