I lived in Spain when I was a kid and I've been to quite a few bullfights in the Plaza de Toros in Sevilla.
I was told that the movements the matador makes with the cape is what gets the bull to charge him.
The red color has nothing to do with it.
I may be wrong because I was a kid when I was told this.
I can tell you that out here in rural Florida where my beef cattle operation is and it's common for people to have cows and bulls, there is at least one consensus.
There is no gate made that is strong enough to contain an enraged bull. When they are placid and not aggressive, a good stock gate does it's job and helps keep them in their paddock.
But if they want to get out or get to something on the other side of the gate, they can destroy the gate in no time.
So there is no such thing as a bull-proof gate. Only city folk think that. :-)
I was always told to freeze...if I can. Otherwise, head for the walnut grove. LOL