This is a particle system created by Jeffrey Ventrella.
All organisms naturally gravitate to other kinds of organisms, and likewise are repelled by other kinds of organisms. These particles experience attractions and repulsions with other particles of different colors. They cluster into social pods, or scatter and flee, often mimicking biological behaviors.
You can play with these clusters live at ventrella.com/Clusters or download the free iOS app from the Apple Store:
More of Jeffrey Ventrella's work can be found at ventrella.com