Well, there were the "FX" motors made by MRC (IIRC) a couple decades ago... Those were pretty cool... Basically they were "smoke generators"-- you had a second launch controller that you fired off the FX motors first, they would sit there chugging away with smoke, and after a few seconds you did your countdown and launched the actual standard-issue rocket motor propelling the rocket with the second launch controller.
Theoretically any of the "effects" chemicals mixed with BP for fireworks could be mixed with BP propellant to create similar effects in the motor (IE different colors, sparks, etc.) Some of them might substantially change the performance of the motor though over the standard BP formulation. Adding sparks to the tracking smoke might be nice (or more tracking smoke for that matter!)
BUT, and this is a biggie... it's not a good idea... and it's the main reason I'm not particularly fond of special formulation 'effects motors' even in larger HPR motors, especially sparkies... they TRULY blur the distinctions between "model rocketry" (or "hobby rocketry" if you prefer) and "fireworks" or pyrotechnics. Most people nowdays have no idea of the history of the long, hard fought battle over DECADES to get model rocketry legally separated from fireworks. With our now more litigious society, increasingly risk averse, ever fearful of terrorists and threats, ever more regulated and increasingly paranoid and intrusive government and neighbors (who feel everybody's business is THEIR business) this is really the wrong direction to take, IMHO. We have enough to deal with just to maintain the status quo WRT regulations and such-- we don't need to blur the distinctions even more and draw more attention to ourselves, IMHO.
Later! OL JR