There are 6 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 (4, 6)
Distance from target shape to blue trapezoid at (4, 0): 6
Distance from target shape to red right_triangle at (3, 5): 2
Distance from target shape to pink rectangle at (5, 3): 4
Distance from target shape to cyan right_triangle at (6, 3): 5
Distance from target shape to orange square at (6, 6): 2
Closest shape is the red right_triangle at (3, 5) with distance 2</think>

<answer>(3, 5)</answer>