You can choose from 4 colors to color every square of the following $10\times 10$ grid.
After you finish, I'm going to take a connected block with at most three colors away. Your goal is to minimize the number of squares I can take away. How should you color the grid?
Two squares are connected if they share a common side. The block in the upper right quadrant is connected, the one in the lower left is not, because the green and blue squares share no common side with any other squares.