Recently, I read a book entitled "Blue and Yellow Don't Make Green" by Michael Wilcox. It is fascinating. I agree with the author. The logic is rather simple. We know a yellow pigment reflects yellow light only and absorbs light of all other colors, and a blue pigment reflects blue light and absorbs the rest. If we mix yellow and blue paints together, the yellow light reflected by the yellow pigments gets absorbed by the blue pigments and vice versa. In consequence, the mixture will reflect no light, and we should see black. With the same reasoning, we can conclude that red and blue don't make purple, yellow and red don't make orange. They all make black only. The whole concepts of primary and secondary colors have been thrown out of the window. Isn't that bizarre? But, you know what, he is right. I can demonstrate this effect in front of you if I see you.
However in our experiences, we all know that blue and yellow do make green. I will talk to you more next time. After reading that book, I spent some time with my own color structure. I made this color wheel last night. The colors was arranged carefully such that the complementaries really make grays. I want to make sure this wheel does provide practical guidance, but not just an illustration of theories.