OpenCV in Python: Rectangle with fill and stroke in one loop

Problem solved

Thanks to feedback from @grismar, I now avoid drawing the solid-line rectangles on the same layer as the transparent fill rectangles, but instead draw directly on the haystack image:

for rectangle in rectangles:
    # Determine the location position.
    top_left = (rectangle[0], rectangle[1])
    bottom_right = (rectangle[0] + rectangle[2], rectangle[1] + rectangle[3])

    # Draw a transparent, filled rectangle over the detected needle image.
    cv.rectangle(scribble_image, top_left, bottom_right, color = (0, 255, 0), thickness = -1)

    # Draw a solid line around the detected needle image.
    cv.rectangle(haystack_image, top_left, bottom_right, color = (0, 255, 0), thickness = 2, lineType = cv.LINE_4)

result_image = cv.addWeighted(scribble_image, 0.25, haystack_image, 1 - 0.25, 0)

# Display the image in a window.
cv.imshow('Result', result_image)