The cache is not located at the posted coordinates.
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.
Start zapping the cells on the following grid by examining the colorful numbers as clues.
Once you're done, examine the leftover cells and with a little bit of imagination, you'll soon see two 3-digit numbers. Call the smaller of the two N, and the other W.
- Divide N by 1000 and add it to the posted North coordinates.
- Divide W by 1000 and add it to the posted West coordinates.
You can check your answers for this puzzle on Geochecker.com.
You can validate your puzzle solution with certitude.
Congrats to billrow on the FTF.