In an interview he gave to Guitar World magazine in July, 1985, Van Halen states that his "brown sound" is "basically a tone, a feeling that I'm always working at...It comes from the person." He continues, "If the person doesn't even know what that type of tone I'm talking about is, they can't really work towards it, can they?"
i believe there is a pedal named The Brown Sound out these days guys....
i guess trying to cash in on VH's thing
And there's also the amazing Mr. ED pedal.