My old former horse, Kainne, the "big fancy Thoroughbred" thought the fireworks were in celebration of how wonderful he is. When they went off he'd perk up and add some prance to his trot, get all proud of himself. Didn't even get scared, just proud.
It's a good summary of his self esteem level. Kainne was born to shine. I can't wait for him to show with his new owner!