Halevi,
You said “The question is that he noticed a color reflecting off an object of a different color. ”
And my answer was that the reason he saw the “other” color when he applied a filter was because the original color he was seeing (when he was shining unfiltered white light) was a mix of more then one of the “primary colors” that make up white light…. (in my example blue and red were being bounced back so he perceived it as purple he was assuming that the red and blue light was absorbed so if he shined a light through a blue filter he was surprised that blue light bounced back, but blue light was being bounced back all along. Now if he had tried to shine a green light on a purple surface the surface would appear more or less black.
It would be the same if you shined light of any one of two primary colors on an object that is the third color for example if you shine a green or blue light on a red surface the surface will appear black as well).
That’s why I was saying that the premise his question is based on is simply wrong.