The title of the event has no separate styling class... it is just a link, so whatever your site template styling for links is, that is what is used. To style links inside of the event listing page separately, add this to the main.css file:
tr.eventListRow1 a:link { }
tr.eventListRow2 a:link { }
Put whatever styling inside of the { } that you need. This will apply to all text links inside of the list table.
If you need to get styling added ONLY to the title, you'll need to modify the code further in file:
/components/com_dtregister/views/event/tmpl/list_row.php
Look for:
<td align="left" class="eventlist">[url=<?php echo $event_title_href;?>]<?php echo $row->title;?>[/url]
<?php }else { ?>
<td align="left" class="eventlist"><?php echo $row->title;?>
<?php } ?>
Where you see $row->title, this is where the title is pulled in. You can add some styling directly into this spot, or you could add a class name to pull in additional styling through the main.css file.