Super Greyscale Brothers
Original title: Super Mario Bros.
Platform: Nintendo Entertainment System
Region: USA (Update Hacks)
Media: Cartridge
Controller: NES Gamepad
Genre: Platformer 
Gametype: Hack
Release Year: 2007
Players: 1 or 2 Alternating
Hacked by: Dave Augusta
Version: 1.0
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Super Greyscale Brothers is a complete palette only hack of Super Mario Brothers 1. Changes the entire palette from nes color to only 6 grey nes variant colors. Darkgrey, Lightgrey, Black, White, Grey2, White2. That is it no other changes. It is however a stand alone palette hack no external palette file is needed just apply the patch and play it in you favorite emulator.

http://www.romhacking.net/hacks/393/