49 cards where the color identity ≤ RUW and the full Oracle text includes “had flash”

Emergence Zone (War of the Spark #245)
Leyline of Anticipation (Commander Legends: Battle for Baldur's Gate #726)
Shimmer Myr (Commander Masters #409)
Sigarda's Aid (Commander Legends #384)
Vedalken Orrery (Double Masters 2022 #317)
Teferi, Time Raveler (Ravnica Remastered #232)
Liberator, Urza's Battlethopter (The Brothers' War #237)
Timely Ward (Commander Legends #363)
Wizards of Thay (Commander Legends: Battle for Baldur's Gate #105)
Borne Upon a Wind (The Lord of the Rings: Tales of Middle-earth #44)
Gandalf the White (The Lord of the Rings: Tales of Middle-earth #19)
Blast-Furnace Hellkite (The Brothers' War Commander #12)
Raff Capashen, Ship's Mage (Commander Masters #351)
Renari, Merchant of Marvels (Commander Legends: Battle for Baldur's Gate #90)
Tidal Barracuda (Commander 2020 #39)
Elsha of the Infinite (Double Masters 2022 #208)
Heliod, the Radiant Dawn // Heliod, the Warped Eclipse (March of the Machine #17)
Heliod, the Radiant Dawn // Heliod, the Warped Eclipse (March of the Machine #17)
Rout (Commander 2021 #101)
Skittering Cicada (Commander Masters #717)
Gandalf, Friend of the Shire (The Lord of the Rings: Tales of Middle-earth #50)
Quicken (Ravnica Remastered #57)
Silver Scrutiny (Dominaria United #65)
Rattlechains (Crimson Vow Commander #110)
Winding Canyons (Weatherlight #167)
Progenitor's Icon (The Lost Caverns of Ixalan Commander #100)
Asinine Antics (Wilds of Eldraine #42)
Najal, the Storm Runner (Dominaria United #208)
Complete the Circuit (March of the Machine #52)
Harbinger of the Tides (Duel Decks: Merfolk vs. Goblins #7)
Hypersonic Dragon (Ravnica: Clue Edition #196)
Breath of the Sleepless (Crimson Vow Commander #11)
Final-Word Phantom (Murders at Karlov Manor Commander #22)
Scout's Warning (Future Sight #16)
Sally Sparrow (Doctor Who #155)
Breaking Wave (Invasion #48)
Ward of Lights (Mirage #47)
Rootwater Shaman (Tempest #84)
Mystic Veil (Visions #38)
Ghitu Fire (Invasion #144)
Dragon Grip (Khans of Tarkir #107)
Parapet (Visions #14)
Lightning Reflexes (Dominaria Remastered #128)
Swift Reckoning (Ultimate Masters #39)
Relic Ward (Visions #16)
Mystical Tether (Outlaws of Thunder Junction #19)
Hungering Yeti (Fate Reforged #105)
Soar (Mirage #93)
A-Teferi, Time Raveler (War of the Spark #A-221)
Shove Aside (Alchemy: Murders at Karlov Manor #16)

Though this query has ended, its relics still slumber in New Argive.