There are 5 shapes on a 8x8 grid. Which shape is closest to the green square in terms of Manhattan distance? The final answer is the grid position of the closest shape like (row_index, column_index).
<think>Target shape: green square at (5, 6)
Distance from target shape to gray square at (7, 7): 3
Distance from target shape to purple right_triangle at (5, 5): 1
Distance from target shape to brown right_triangle at (6, 1): 6
Distance from target shape to blue square at (5, 3): 3
Closest shape is the purple right_triangle at (5, 5) with distance 1</think>

<answer>(5, 5)</answer>