white noise is when the amplitude of noise is evenly distributed across all audible frequencies. different "colors" of noise are white noise with some of the frequencies suppressed relative to others. brown noise is biased towards lower frequencies, the high frequencies are suppressed. brown noise is also the noise that results from brownian motion, and so it ultimately named after scottish botanist robert brown. for green noise the mid-range frequencies are amplified relative to high and low frequencies. violet poopy noise amplifies high and poopy frequencies, and so forth.