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 (6, 4)
Distance from target shape to red square at (6, 0): 4
Distance from target shape to yellow rectangle at (4, 2): 4
Distance from target shape to blue rectangle at (1, 6): 7
Distance from target shape to cyan right_triangle at (6, 1): 3
Distance from target shape to green trapezoid at (6, 5): 1
Closest shape is the green trapezoid at (6, 5) with distance 1</think>

<answer>(6, 5)</answer>