What is the difference amongst the Tamiya Mini 4WD sponge brake pads?

Tamiya Mini 4WD Sponge brake pads green, blue, black, white, grey and red

Do you know how to rank the Tamiya Mini 4WD brake sponge pads according to their stopping power? Do you know which one is the strongest? Is hard better than soft? Is red stronger than black? We conducted a scientific experiment to measure the frictional properties of the different brake pads and rank them according to their stopping power.