Some questions

[Digital Jedi]

I vaguely recall an avatar mod that used the/a ranking system. Try a Titles Only search of just the word "avatar" for 3.8 mods. Unless I'm crazy and remembering something else, it should turn up there.

By adding a custom field, do you mean outside of vB's inherent ability to do this? Or are you looking to add custom fields' output to a particular part of the forum?

In the postbit_legacy template, you can find all the blocks of code for each of those fields. You can color them by adding style="color:name" to the strong tags. Ex: $post[postcount] is, well, Post Count.

			<if condition="$show['postcount']">#<a href="showpost.php?$session[sessionurl]p=$post[postid]&amp;postcount=$post[postcount]" target="new" rel="nofollow" id="postcount$post[postid]" name="$post[postcount]"><strong style="color:red">$post[postcount]</strong></a></if>
			<if condition="$show['inlinemod']">

You can use the color name, or the color code number. Ex: color:#FFFFFF would make the text white.