Found some values that give a good dynamic range from an fBm node, so tried replacing the Noise node with an fBm and plugged that into the Red input of a User_Defined node. Added a second and third fBm node to drive the Green and Blue, tweaked the x/y/z_index values in them to get a different pattern from the first. Now I have the complete range of colours available for the tiles:

Works in both FireFly and SuperFly, without those FireFly/Noise artefacts:

 

(note: the u-derived value is plugged into x_index, and the v-derived value into y-index and z-index. Using a constant produces the same problem as before)

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The 3Dcheapskate (also available in DAZ and HiveWire3D flavours) occasionally posts sensible stuff. Usually by accident.
And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU.