I'm sorry, you could be right, but walk me through here.

If I pay an artist with brush-canvas-and-palette to mix red and white such that he can arrive at a color that is the average of the quantities of red and white on the Switzerland flag, are you saying he couldn't do that by eyeballing it?

Or are you saying he couldn't do that mechanically automatically by just mixing the exact amounts of red and white on the Switzerland flag without eyeballing it?

If you're saying the latter, that it's not automatic and the proportions are not the same as on the original flag, I could believe you, but you haven't said anything that would cause me to believe that.

If you're saying the former, there's no way I can believe in that, because then every art book on colors would have to make a major pause in explaining colors to tell me what you're trying to tell me, and no art color book does that.

Therefore it seems to me that brush-canvas-and-palette artists can totally do what you are saying can't be done - otherwise how were all the paintings that the world has accumulated in museums painted?