CMYKraft takes the original textures from the game and reduces the colors to only cyan, magenta, yellow, black, and white in 64x textures!
Most blocks will still look about the same if you just look from a distance...
Alternatively, CMYKraft Lite keeps all the same modified block and item textures, but removes most of the modified UI textures, making it easier and more comfortable to navigate UIs in the game. I would highly recommend this version if you plan on really playing the game with this pack.
NOTE: This pack may give some people headaches, please be careful and use your best judgement while using it.