We've had flashback in many a color since it's printing, and many of these cards have been powerful in any number of formats
Which One Should You Choose
The full art trainer from a set that's gone out of print
Well, it doesnt always have to be a bad card, but its one thats caught your eye, and a card that you think is good enough to see play, often at a time when its not getting any attention
While the majority of permanents in multicolor decks tend to be monocolor aside from in specific color combinations and strategies, this is still functionally a Ravnica at War that sometimes does a bit more, which is cool
Waterfront Bouncer, Trickster Mage, and maybe Alexi, Zephyr Mage are passable tempo options, Stronghold Biologist and Stronghold Machinist are more color-heavy, and Dreamscape Artist hits color fixing and ramp, unusual for blue