Using the mozaic texture mode, the shader picks a colour from the pixel group of the texture which is applied to the tile.
Tinting the Hi and Low tints to randomly apply the colour between the chosen tints. A normal map is appled to give a slight roughness.
A rock texture and normal map is used to create the paving tile pattern. This uses the Mega texture mode which randomly selects part of the texture and applies it to each tile removing the repeat tiling you would get from tiling textures.
CrazyPaving Shader
(Project in Unity Asset Store submission.
Unity surface shaders for dynamic real-time rendering of crazy paving and mosaic tiling.
It uses Voronoi to create the tiles so is suitable for stain glass windows, crazy paving, mosaic art floors and walls, dragon or creature skins, dry mud patterns plus a lot more.
Fully configurable, procedurally calculates correct normals, edges etc.
Refer to the .pdf documentation for full details.