to customize one of your boxes just make a class for it in your css
for example
CODE
<style>
.boxclass1
{
border: 7px solid #COLOR;
}
</style>
you can also add any other modifications youd like. and then in the html put these tags around your box code
CODE
<div class="boxclass1">
the box
</div>
well, thats the way i'd do it any way
heres another way, its probaly more accurate for the code you're using for your box
CODE
<div style="width:100px; height:100px; border:7px #COLOR solid;>yeah, here is my box</div>
//edit
or are you asking for different colored borders around your default boxes? if you are i only know how you could do that for you contacts box
CODE
<style type="text/css">
.contactTable table, table.contactTable td { padding:0px !important;
border:7px solid #COLOR;
}