A light show was a display of colorful light such as lasers, typically performed for entertainment purposes. Around the time of the Nikardun conquests, light shows had been adapted into a naval tactic, where a naval force would put on a show of attacking while doing little to no actual damage.
In about 18 BBY, Senior Captain Thrawn of the Chiss Ascendancy encountered a force of the Paataatus Hiveborn above their homeworld of Nettehi. In the ensuing skirmish, Paataatus warships aimed their spectrum lasers at the ships of Thrawn's Picket Force Six. However, the Paataatus forces' spectrum lasers were configured to deal no damage, even though spectrum lasers were designed to shift their energy frequencies to maximize damage to whatever material they were targeted on. This led Thrawn to discover the Paataatus were subjugated to remnants of the Nikardun Destiny's military. Thrawn's first officer Mid Captain Ufsa'mak'ro remarked that the Paataatus were putting on a "light show" rather than attacking the Chiss. The Prince Militaire of the Hiveborn was in fact covertly requesting Thrawn's help to free his people from the Nikardun. In the ensuing skirmish above Nettehi, Thrawn targeted Nikardun blockade frigates effectively holding Nettehi hostage, and the Paataatus leader thanked Thrawn for his assistance.
The Watith Captain Fsir later used the tactic by having his own remotely-piloted gunboats attack his freighter during a skirmish meant to lead Thrawn to believe they were under attack by Vagaari pirates. Thrawn captured and appropriated the Watith gunboats and the Saltbarrel, which he would in turn use for a light show of his own. At the Hoxim incident, Thrawn sought to foil a scheme to draw the Ascendancy into a civil war. There, Thrawn had members of three Great Families target their family fleets' warships with "maximum ferocity but minimal actual damage" using the remote-controlled ships he had claimed from the treacherous Watith.
Light shows first appeared as a naval tactic in the 2021 novel Thrawn Ascendancy: Greater Good by Timothy Zahn. That novel is the second of Zahn's Star Wars: The Ascendancy Trilogy.