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

<answer>(6, 7)</answer>