I have little knowledge of color theory and chemistery. Recently I came to know that printers use CMYK colored inks and combine them in different proportions to achieve any color on print.
Let us suppose I fill white paper fully with red sketch then white light will fall on inked surface and all colors(wavelengths) except red will be absorbed and only red will be emitted/reflected. Good. Now I overfill that paper with green sketch. Now two things can happen:
Both the inks of sketches mix but do not interact molecully. Like two chemicals A and B mixed in water and both A and B are everywhere in water but they are still distinct molecules. A's and B's molecules don't react chemically.
Both the inks of sketches mix and interact molecuelly. Like HCL and Na2SO4 are mixed in water and they react molecually to make h2SO4 and NaCl.
Now if 1 is true then on any point on paper's surface I have two types of molecules, 1. that reflect red light and 2. that reflect green light. So when white light will fall on paper then from every point two colors will be reflected, red and green. When they'll reach someone's eye then the perceived color will be red+green = yellow. So inks should make additive color.
On the other hand if 2 is true then molecules of red and green ink will react chemically to make a new kind of compound. Now it is not necessary that the new kind of compound absorbs both red and green. It could emit/reflect any random color. So the paper could be of any color depending upon the chemical formula of inks used. So in this case too inks don't make subtractive colors.
Sadly in reality inks make subtractive color and the color of paper actually is dark brownish black not bright yellow. So in reality the mixed ink absorbs almost all colors including red and green which were remaining.
So my question is why does both red and green got subtracted from the mixed ink? In general why does mixture of inks produce subtractive color rather than additive?