It seems like the suggestion is that they're color blind, and they can't tell the difference between red, yellow, and green.
The problem is that the text clues give you almost no information to work with
This, exactly this. Hat's off to you.
The main idea is being blind to specific colors. All the doors and hints will either lead you to a correct color that could be seen by a being with this specific color vision or the right door will be selected by exclusion. As an example, if the hint is to use the red door and you can see grey, blue and green. The grey should be the correct "red" door by exclusion.
The issue is that some of the clues are too vague.
For example once of the rooms says "green was never one of our colors", and there is a gray, blue, or green door. However, green appears gray when you activate the orb, and the blue door doesn't lead to progress.
The final clue is something like "you are not one of us" and every door leads to the orb room.
I just checked and looks like you mixed up something. The room with "green was never one of our colors" has red, blue and green doors. The orb lets you know that the "true" vision doesn't discern neither red or green. So, in the end, they would see 2 gray and 1 blue door. Since there's no way to determine which of them may be green that you can't use, the only option left is the blue door.
As for the progress, the puzzle is tricky. In the example above, you picked the blue door, but it looks like you ended up in the orb room. This means you made a mistake before. This trick is in so saving after each door won't help you that much.
Yes, the final room with that plate is not a test room. You made a mistake somewhere before, so all the doors will lead you to the orb room.