Answer: you would see an afterimage of a flag with the opposing colour systems(blue,black and red in middle), then white surface of the paper
Explanation: The opponent-process theory states that the cone photoreceptors are linked together to form three opposing colour pairs: blue/yellow, red/green, and black/white and the activation of one member of the pair inhibits activity in the other.
So after staring at a white sheet of paper for a minute, the yellow, white and green parts of the three opponent-process systems would be fatigued and unable to oppose the blue, black and red parts of these systems when you stare at the white sheet of paper. Therefore after seeing white, you would see an afterimage of a flag with alternating blue and black stripes and a block of red in the middle. Once the opposing parts of the three systems recovered, the flag afterimage would disappear and you would then see the white surface of the paper.