How many ways are there to place 3 indistinguishable red chips, 3 indistinguishable blue chips, and 3 indistinguishable green chips in the squares of a 3 \times 3 grid so that no two chips of the same color are directly adjacent to each other, either vertically or horizontally?

**Answer Choices**

A. 12

B. 18

C. 24

D. 30

E. 36