let obs = new MutationObserver(async (records, _) => {
var a = []; $('#box span').each( function(){
a.push(this.style.backgroundColor)
})
for(i = 0 ; i< a.length ; i++){
if(a.indexOf(a[i]) == a.lastIndexOf(a[i])){
$('#box span').eq(i)[0].style.backgroundColor = "#fff"
}
}
})
obs.observe($('#box')[0], { childList: true, subtree: true });