I have been trying to recreate a good looking procedural mold texture for a bit now.
I have found the best approach to creating the actual round shape of the mold patches seen in the pic seem to be utilizing the Voronoi texture as bump and color in a principled shader, then using a mix shader with the Voronoi texture as factor to apply the mold over whatever material I want.
There are however 2 big problems I have run into, first problem is the colour, mold as shown in the picture remains a pretty solid color until the edge where it quickly fades to white, I have not found a way to give every individual cell this color composition.
The second problem I have is that I can't figure out how to increase the space between the cells to the extent that they are in the pic below.
If you feel that you know of a better or nicer way to replicate this than what I currently have please advise.
Mold in petri dish, note how the edges fade to white.