You might be able to do this with some creative use of tokens and CSS
This technique uses the fact that when tokens change, searches which use those tokens are refreshed
Initialise the tokens with complementary colours and zero counter
<set token="flashinterval">0</set>
<set token="flashcolour">000000</set>
<set token="flashback">ffffff</set>
Start with a hidden panel which swaps foreground and background colour tokens and increment a count token - the swapping (and incrementing) is limited (to 10 in this instance) so the attention grab eventually stops.
There is also some hidden CSS to implement the colour changes.
The panel being changed resets the counter when the search completes (after refreshing)
<panel depends="$stayhidden$">
<table>
<search>
<done>
<set token="flashcolour">$result.colour$</set>
<set token="flashback">$result.back$</set>
<set token="flashinterval">$result.interval$</set>
</done>
<query>| makeresults
| eval colour=if($flashinterval$<10,$flashback|s$,$flashcolour|s$)
| eval back=if($flashinterval$<10,$flashcolour|s$,$flashback|s$)
| eval interval=if($flashinterval$<10,$flashinterval$+1,$flashinterval$)
| table colour back interval</query>
<earliest>-24h@h</earliest>
<latest>now</latest>
</search>
<option name="drilldown">none</option>
<option name="refresh.display">progressbar</option>
</table>
<html>
<style>
div[id="flash"] tr[data-view$="ResultsTableRow"] td:nth-child(1)
{
color: #$flashcolour$ !important;
background-color: #$flashback$ !important;
}
</style>
</html>
</panel>
<panel>
<table id="flash">
<title>Flash</title>
<search>
<done>
<set token="flashinterval">0</set>
</done>
<query>insert your search here</query>
<earliest>-24h@h</earliest>
<latest>now</latest>
</search>
<option name="drilldown">none</option>
<option name="refresh.display">progressbar</option>
</table>
</panel>
