You have to connect something to the One Sided Square.  Click on the little Socket thing at the side of Diffuse_Color, hold the mouse button and drag it out.  You'll see a cable and a popup.  Select Tile from the popup list.  

You'll then have a node to work on.  You can change the tile colours, sizes and various other properties.

You can add a black and white version to the Bump or Displacement channels, and maybe play around with Alternate_Specular to give your tiles a glossy look. 

Coppula eam se non posit acceptera jocularum.

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