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 (7, 4)
Distance from target shape to brown rectangle at (6, 4): 1
Distance from target shape to green rectangle at (3, 3): 5
Distance from target shape to gray right_triangle at (3, 0): 8
Distance from target shape to orange trapezoid at (4, 6): 5
Distance from target shape to cyan rectangle at (5, 5): 3
Closest shape is the brown rectangle at (6, 4) with distance 1</think>

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