Actually bulls see in black and white so color has no affect other than tint of the color. If you waved a blue flag they would chase you as well. It is just the movement.
Totally not the bulls fault. Those bulls are bred to fight and attack everything that you put in front of them.
It's sad what people put them threw. So sad. Those horses didn't deserve to be there and killed like that.
It's kind of like people training pit bulls to be fighters.