A blue belt should be able to work in a team and execute his part of the work well, integrating it right The purple belt can do the same but alone, developing

A blue belt should be able to work in a team and execute his part of the work well, integrating it right The purple belt can do the same but alone, developing a whole project by himself taking care of the important things, scale it to commercial use And a black belt will managing the work of multiple purple belts to do what they do well at a large scale