During overland travel of some kind --
Far too close for comfort, there is a series of small but loud and COLOURFUL explosions -- smoke, flames leaping into the air but not catching anything on fire, pinwheels of wind -- and then relative quiet.
If the party investigates, they discover a splintered wagon still hitched to two stunned, and ridiculously technicoloured, mules. Scattered all around is wood, metal fittings, and countless shards of broken crockery that contained an enterprising mage-chymist's stash, as well as the flabbergasted brigands who tried to raid the wagon.
The brigands are also mottled in bright, ridiculous colours. A few are starting to shed glitter. All around the wagon, the reagent-soaked soil and greenery is starting to come together into dozens of small, glittery, colour-splotched critters, sort of like fancy grass-furred baroque homunculi.
Eventually the shock's going to wear off everyone --
If the party doesn't investigate, the brigands will retreat (still marked by the explosion, which may have further effects), the mules kick themselves free (or are taken by the brigands), and the homunculi spread out across the countryside, possibly to make more of themselves, possibly to spread wild colours, possibly to root into the ground, who knows ~?
(where is the mage-chymist? turned into a flappy bird-bat and fled in surprise. she'll get herself together in a day and then oh boy)