The style selector needs to be repeated for all columns apart from the first (index="0")
<panel depends="$stayhidden$">
<html>
<style>
#tableClickableColumn table tbody td[data-cell-index="1"],
#tableClickableColumn table tbody td[data-cell-index="2"]{
color: black !important;
}
</style>
</html>
</panel>
<panel>
<table id="tableClickableColumn">
<search>
<query>
Put your search here
</query>
<earliest>-24h@h</earliest>
<latest>now</latest>
</search>
<option name="drilldown">cell</option>
<option name="refresh.display">progressbar</option>
<drilldown>
<condition field="first column name">
<link target="_blank">$click.value|n$</link>
</condition>
<condition>
</condition>
</drilldown>
</table>
</panel>
