spray/paint effect - how to?

How to make this spray effect like seen in this video ? the author gave some indication in the commentary section but I can't figure out the node trees :

https://www.instagram.com/p/CyOrYPHxlav/



You can dynamically like I do on the setup, or manually through weight painting (blurring and normalizing the weight can be helpful), mark the time of paint applying, then make a copy of the mesh, displace it based on that time, and make the most displaced vertices transparent:



Imgur mirror (SE image hosting has problems)



Imgur mirror



To avoid z-fighting, I'm making the paint to go down to 0.001 of displace instead of 0, but you could instead/additionally (as the 1‰ is a workaround that will fail with far enough camera/wide enough clip range) also store the attribute on original mesh and use it to transition the pink color to yellow to synchronize the overlapping faces colors.