styling question about color of a single menu item

Hi famewebdesign!

what you could try is this:
At first set the main background-color for your whole menu to transparent:

#top #header .av-main-nav > li > a {
background-color: transparent;
}

Than you are able to define a custom color for each menu:
For your “afspraak” menu use this:

li#menu-item-86 {
background-color: green;
margin-right: 10px;
}

For the rest of the menu use your normal color:

li#menu-item-87 {
background-color: #30b9db;
margin-right: 10px;
}
li#menu-item-88 {
background-color: #30b9db;
margin-right: 10px;
}
li#menu-item-89 {
background-color: #30b9db;
margin-right: 10px;
}
li#menu-item-90 {
background-color: #30b9db;
margin-right: 10px;
}

Hope this is what you need!

Cheers!
Andy