There are 6 shapes on a 8x8 grid. Which shape is closest to the green 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: green right_triangle at (5, 4)
Distance from target shape to blue square at (5, 0): 4
Distance from target shape to brown square at (3, 0): 6
Distance from target shape to cyan trapezoid at (2, 3): 4
Distance from target shape to pink trapezoid at (0, 4): 5
Distance from target shape to purple right_triangle at (0, 7): 8
Closest shape is the blue square at (5, 0) with distance 4</think>

<answer>(5, 0)</answer>