Bulls are colour blind.The color red DOES NOT make bulls go crazy.
Ever see those Bugs Bunny cartoons where Bugs would paint something red and a bull would go crazy and charge at it? Turns out that wouldn't work.
The Mythbusters tested this one out and found that the bulls were just as likely to charge at white flags and blue flags as they were to charge at red ones. The bulls also ignored a guy dressed in red who stayed motionless. Turns out that bulls just charge at whatever moves the most, regardless of color.
This makes sense, since bulls wouldn't be able to tell if a cape or a flag was red anyway. Bulls are colorblind. Besides, in the middle of a bullfight, the bull is probably more mad about having a bunch of guys stabbing him with spears than he is about the color of the matador's cape.