This is like putting three layers of paper on top of eachother.
The bottom layer (box1) is red.
The middle layer (box2) is blue.
The top layer (box 3) is transparent.
Obviously, in this situation, you will see BLUE. And the only way to see the red, is when the two top layers (box2 and box3) are BOTH transparent.
If you can’t change box2, then there’s no way to make box1 visible.