I had the same problem as changing the css meant that other lines were invisible.
The texts can be found in messageindex.php:
Find:
<tr>
<td align="left" valign="middle">
<img src="$imagesdir/hotthread.gif" alt=""> <font size="1">$txt[454]</font>
<BR><img src="$imagesdir/veryhotthread.gif" alt=""> <font size="1">$txt[455]</font>$stickylegend$polllegend</td>
<td align="left" valign="middle">
<img src="$imagesdir/locked.gif" alt=""> <font size="1">$txt[456]</font>
<BR><img src="$imagesdir/thread.gif" alt=""> <font size="1">$txt[457]</font>$lockedstickylegend$lockedpolllegend</td>
<td align="right" valign="middle"><form action="$scripturl" method="GET">
<font size="1">$txt[160]:</font>$selecthtml</form></td>
</tr>
and replace with (for example, choose your own colors)
<tr>
<td align="left" valign="middle"><font size="1" color="#FFCC99">
<img src="$imagesdir/hotthread.gif" alt=""> <font size="1" color="#FFCC99">$txt[454]
<BR><img src="$imagesdir/veryhotthread.gif" alt=""> <font size="1" color="#FFCC99">$txt[455]$stickylegend$polllegend</td>
<td align="left" valign="middle">
<img src="$imagesdir/locked.gif" alt=""> <font size="1" color="#FFCC99">$txt[456]
<BR><img src="$imagesdir/thread.gif" alt=""> <font size="1" color="#FFCC99">$txt[457]</font>$lockedstickylegend$lockedpolllegend</td>
<td align="right" valign="middle"><form action="$scripturl" method="GET">
<font size="1" color="#FFCC99">$txt[160]:</font>$selecthtml</form></td>
</tr>
Ok, I am not a neat coder and forgot all </font> tags,
but it should do the trick!
(check out
http://www.7summits.com/yabb/index.php?board=10 for an example of the result.
Good luck,
www.7summits.com