Bluish Paper Test Help

I'd like to ask you about some tests I've been doing on bluish paper... I know it's probably not bluish paper, but perhaps it could be... In the normal test on orange cardstock, where the stamp stands out as more opaque than the other two examples, one light-toned and the other darker, I added my phone's flash from underneath the card to check the opacity. The result is that the supposed bluish paper is considerably more opaque, as the reddish intensity is much lower compared to the other two. In the photos, you can see how the light passes through the common examples with such force that it damages the camera lens, while the supposed bluish paper softens the light... What do you think about this?

No bluish..single watermark

I think this is unscientific and meaningless. Sorry.

you can see how the light passes through the common examples with such force that it damages the camera lens
That is a rather humorous idea. It takes a lot more to damage a lens (even a cheap one). Throwing off your camera from a building might do the trick, but not shining light at the camera. The worst thing that could happen is you oversaturate the chip in the camera so it is blinded for a few seconds.

Your test is completely pointless. The results will depend on whether the stamps lies flat on the orange cardboard, whether the stamp has aged or not, the distance of your flash light to the stamp, whether you drank milk for breakfast, and whatnot.

Bluish paper is actually grayish with 1/3 rag content.

I applaud your effort to show us something. However, I don't see it. Sorry

It lacks a credible theory to be tested. It, also, completely lacks a controlled environment.
The moment the paper thickness was not uniform, the test fails even under controlled conditions. And that, even, is before raising the subjects drkohler raised.

Also, you would need multiple examples of confirmed bluish paper stamps to perform this test.