I don't really know why you want to do things this way.
You could simply use the id selectors:
#city { background-color: red; }
#state { background-color: green; }
#zipcode { background-color: blue; }
If you want to specify by class then assuming your <li> has a class of className you can use a number of pseudo-selectors to access the children
DEMO: http://jsfiddle.net/8qAvb/
HTML
<li class="className">
<div id="city">city</div>
<div id="state">state</div>
<div id="other1">other1</div>
<div id="other2">other2</div>
<div id="other3">other3</div>
<div id="other4">other4</div>
<div id="zipcode">zipcode</div>
</li>
CSS
.className > div {
background-color: green;
}
.className > div:first-child {
background-color: red;
}
.className > div:nth-child(3) {
background-color: lime;
}
.className > div:nth-child(4) {
background-color: pink;
}
.className > div:nth-child(5) {
background-color: orange;
}
.className > div:last-child {
background-color: blue;
}
CSS :nth-child()