I understand your black vs. white analogy: if all colors exist at all levels of brightness, then both white and black must exist. But brightness exists on a continuum. Many things exist as discrete forms or concepts:

Suppose I give you a small sealed box, and I tell you that I may have put a marble in it. You can’t touch it, x-ray it, etc. What can you say about the contents of the box?

----- Here’s one of many true statements about the box: EITHER the box contains no marbles OR the box contains at least one marble.

----- Here’s another more general statement: EITHER the box is empty OR the box is not empty.

Do you see the difference between this and your analogy? Non-existence doesn’t require existence to be true. As another example, it is always true that “either Santa Claus (as I define him) exists or Santa Claus does not exist”. This is not a dualistic mind trap. The counterpart to Santa Claus existing is Santa Claus not existing. With discrete phenomena such as this, there is no paradox, no mind trap.