atrapado & jws if I missed yr reply ...
I just checked back in here.
I was referring to the picture as an illustration. It is my understanding by the context, that the purpose is a VISUAL examination. So we are talking apples and oranges, as far as I can tell.
You are explaining how the colours can be created on a computer, and I am seeing it from a material, in-my-hand artist's point of view. I am aware of the RGB of which you speak, since way back when we had big screen televisions in the 80s, and the image was projected, using an RGB format. However, that, imho, would not apply to the example, which was (as I read it) meant to be a visual illustration of someone's point.
The question at hand was .... can you tell when the blue becomes red? It was not posited to a room full of computer techies. I read the question to mean 'by examining it with your EYES'.
t