Using attributes that are created during the groom process can be very useful and beneficial to the look of the asset. we can use attributes like clump ids to add per clump variance to help sell the organic feel of the asset.
we can also use other attributes such as the primitive id to create variance on a smaller level, adding variance to individual hairs. Most animals have about 5-20% of black and white hairs in their coat so we can replicate that by making a probability shader.
When it comes to the main coat colour, we can texture a colour map in mari/substance and use this to drive the main colour. We can use the implicit UVs to change the colour on a strand of hair. For a fox the root and the tip both are black with the orange shades in the middle. we can set the root and top to black then have all the orange and yellow tones driven by our texture map to provide greater variation and get a more accurate and physically plausible shader.
Here is the final shader graph for the asset and as you can see, besides the diffuse colour map, the rest of the shader is procedural.