The Subunit Node Group allows you to separate units in your texture or has a color system similar to Voronoi.
The Node Group works procedurally with the Mapping and the Outputs of the Texture Coordinate Node.
Different Shapes are supported like Hex or Trapeze. (Presets are included; examples are in the image gallery)
When you work with Image Textures and the Node Groups to reduce lines between areas, it helps to set the Texture Interpolation to Closest or use a different Texture Coordinate Output like Object (changes the coordinates too).
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Example Usage (Hex Animation):
It works in Cycles and EEVEE.