There are 6 shapes on a 8x8 grid. Which shape is closest to the red 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: red right_triangle at (6, 4)
Distance from target shape to brown right_triangle at (6, 0): 4
Distance from target shape to pink square at (3, 6): 5
Distance from target shape to purple rectangle at (7, 0): 5
Distance from target shape to cyan trapezoid at (2, 3): 5
Distance from target shape to green square at (6, 5): 1
Closest shape is the green square at (6, 5) with distance 1</think>

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