> the area with the color they can't see gets a lot darker
Interestingly, for me (deuteranomolous) the colors I can't see often seem lighter. For example, green traffic lights appear white. I assumed this is because I can still see the light, it just doesn't get interpreted as green, but I don't know whether that's true.
Green lights are white to me as well, I guess they have a decent chunk of blue in them and people call them green due to the lack of red. (I see blue + green as white since I don't see red)
But if you see it as white as well then I'd expect your problem to be with the color red and not the color green.
Interestingly, for me (deuteranomolous) the colors I can't see often seem lighter. For example, green traffic lights appear white. I assumed this is because I can still see the light, it just doesn't get interpreted as green, but I don't know whether that's true.