I dont know about phpbb2, but if your looking for a template system I remcommend FastTemplate. Very userfriendly. An example for your request would be something like this.
TPL FILE: hime.tpl
<font face=arial color={COLOR1}>hi</font><br>
<font face=arial color={COLOR2}>me</font><br>
PHP FILE: hime.php
<?
include "class.FastTemplate.php3";
$tpl = new FastTemplate("./templates") // Dir that holds your template files
//define the files that you are going to use
$tpl->define( array( hime => "hime.tpl" ));
//Now we can assign colors
$color1 = "CCCCCC";
$color2 = "FFFFFF";
//Lets assign those colors to our template page
$tpl->assign(COLOR1,$color1);
$tpl->assign(COLOR2,$color2);
//Lets parse the page
$tpl->parse(PAGE,"hime");
$tpl->FastPrint(PAGE);
?>
Hope that helps.
Cheers
John