ludo974
I added a class called bluemenu in 'Extra class' field as my above screenshot for the second menu item on your site
you can add custom css rule for this class as below:
.navbar-default .navbar-nav > li.bluemenu {
background-color: #1bd7d0;
}
.navbar-default .navbar-nav > li.bluemenu > a {
color: #ffffff;
}
.t3-megamenu .nav > .dropdown.bluemenu > .dropdown-toggle .caret {
border-top-color: #ffffff;
border-bottom-color: #ffffff;
}
It will look like this:
It's my sample only, you can change the color to suit your need.