Zapping any arbitrary cell in the grid will remove the region containing the zapped cell. A region is defined as one or more cells with the same color and adjacent to each other (two cells are considered adjacent to each other only if they share a side, not just corners). After each zap, the removed space will be occupied by the cells above it due to gravity.
Refer to this puzzle cache for an example.
Click image to interactively play with it.
Now, do a series of zaps on the above grid in the order of the following clue, ... if you zap correctly, after the final zap, the grid should be perfectly cleared.
FTF Prize: $5
Congratulations to Nylimb who's first to solve, and to FTF-ers: jeremiahsjohnson and nezly400
You can validate your puzzle solution with certitude.