system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - What happens when an artist mixes paint for a painting? Are the pigments actually changing physically/chemically? What is actually happening to make the paints change color?
gpt
The pigment particles in the paint are ground incredibly fine.  When two paints are mixed, the two different pigment particles are mixed together and so closely that our eyes can't distinguish one from the other but perceive a new color, of them mixed. 

Picture if you had a million red pingpong balls, and a million yellow pingpong balls, and you mixed them together in a giant pool and looked at them from miles above.  Your eyes couldn't pick out single balls, it would look orange.  

Lets say you mix some red and yellow oil paint together to make an orange paint, and put it under a microscope.  You would be able to see individual red and yellow pigment particles, but the smear of paint on the slide would look orange.