There are 6 shapes on a 8x8 grid. Which shape is closest to the gray 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: gray right_triangle at (6, 4)
Distance from target shape to yellow rectangle at (0, 1): 9
Distance from target shape to brown right_triangle at (1, 7): 8
Distance from target shape to green right_triangle at (5, 4): 1
Distance from target shape to cyan right_triangle at (0, 5): 7
Distance from target shape to orange rectangle at (6, 2): 2
Closest shape is the green right_triangle at (5, 4) with distance 1</think>

<answer>(5, 4)</answer>