When the initial density of black cells goes above 0.5, there is a sudden transition from a final state that is dominated by white to one that is dominated by black.
This Demonstration shows the final state of a 2D cellular automaton after the specified number of evolution steps. After enough steps, the system reaches a state where black or white cells tend to dominate, depending on whether there were more black or white cells in the initial condition. The specific configuration of the initial state does not affect the final state very much, except when the initial density of black cells is very close to 0.5.