Also, what "large bar" do you mean? The rectangle which is black in the gamma is always the same color as the big horizontal one, and same as little vertical one above that. These are rectangles, showing mixture. The ones going from the handles are either only red or only blue.
The goal is to make mixture color be in line with the rest of the gamma. It should not be the same as the one on the right or one on the left. They may sometimes look visually same, but actually they are not, if the game catches a win state.