There are 3 shapes on a 8x8 grid. Which shape is closest to the purple right_triangle 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 right_triangle at (3, 6)
Distance from target shape to cyan square at (1, 4): 4
Distance from target shape to yellow square at (0, 6): 3
Closest shape is the yellow square at (0, 6) with distance 3</think>

<answer>(0, 6)</answer>