djonA,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
.main .child:nth-child(n+3) {
color: red;
}
</style>
</head>
<body>
<div class="main">
<div class="child">1</div>
<div class="child">2</div>
<div class="child">3</div>
<div class="child">4</div>
</div>
<div class="main">
<div class="child">1</div>
<div class="child">2</div>
</div>
</body>
</html>