Unless you employ Jquery/Javascript a bit more on the heavier side than just a few lines or two, I typically just use pure CSS. You can use scripts to change a few things, or even append new classes, but I typically suggest getting comfortable on the CSS/HTML side of things before considering on how to add/augment your code with script.

You can utilize forum IDs, or even category IDs and wrap your forums with a blanket div, and declare different styles using them.

e.g. Assuming that the '.forum' class is containing the forum row code/template, and assuming that you've wrapped your forum rows with a parent div with the cat id in it... this will mean all category 1 forums will have a blue background, and all category 2 forums have a red background.

#cat1 .forum { background: blue; }
#cat2 .forum { background: red; }


If you want to call out individual boards, then you employ the forum id variable.

An example of what the code would look like in the HTML Templates for Forum Rows:
<div class="forum-row" id="forum<!-- |forum_id| -->">FORUMROWS</div>


And then in the style sheets:
#forum1.forum-row { background: yellow; }

This would mean the very first forum (with the ID of #1) will have a yellow background. 

Of course, this is just a very basic gist of things. You would need to make exclusive statements for most if not all div elements that requires its own unique situation.