In Hawaii, Prof James Mitose of Kenpo Jujitsu wore a black gi, while the students wore white gi's. Prof Mitose's student Prof William K.S. Chow wore a black gi, while the students wore white gi's. Prof Chow's student Sijo Adriano Emperado created Kajukenbo and in the beginning, everyone in Kajukenbo wore white gi's. During the mid 1960's, Sijo Emperado asked Kajukenbo practitioners to dye their uniforms black in order to show respect for Chinese martial artists, who created Gung-fu techniques which went into Kajukenbo. Chinese martial artists traditionally wore black uniforms.
After Kajukenbo people adopted black gi's, practitioners of Ed Parker's American Kenpo adopted black gi's. Eventually, a lot of Kenpo styles adopted black gi's and other martial arts adopted black gi's also.
Yes, faded black gi's look cool, you do look tough wearing them. But toughness is inside you, and not determined by the color of your gi. Either you are tough, or you are not. The gi doesn't change anything. In the Kajukenbo schools that I have trained in, the instructor always tells the new student, buy a gi only if you like Kajukenbo and you want to continue training in it. The majority quit and never came back, at least they did not waste money buying a gi. And some beginners did buy a black gi, and they quit anyways. So having the black gi alone does not make any more "hardcore combat" ready.
Having said that the hardcore and extremely hardcore Kajukenbo schools wear black gi's. So do the people who train in the Kajukenbo McDojos. And so do the people who train in the notorious Cerio and Villari Kempo schools. The black gi's do not make the Cerio and Villari people any more "hardcore combat" trained.
And I have seen Kajukenbo schools where they wear white gi's. To me, they stand out because they are supposed to be wearing a black gi, but we live in a free society, I guess any school can choose whatever color gi they want. The most important thing is good quality training.