There are 4 shapes on a 7x7 grid. Which shape is closest to the purple rectangle in terms of Manhattan distance? The final answer is the grid position of the closest shape like (row_index, column_index).
<think>Target shape: purple rectangle at (6, 5)
Distance from target shape to brown rectangle at (1, 2): 8
Distance from target shape to red right_triangle at (6, 2): 3
Distance from target shape to green right_triangle at (6, 4): 1
Closest shape is the green right_triangle at (6, 4) with distance 1</think>

<answer>(6, 4)</answer>