Some differents phenomenons that we can to observe.After to have isolated the colors in a neutral environment, to set the red next to blue, creates a little optical illusion.
If the blue is on the top while the red is under, the optical illusion is a white line.
If the red is on the top while the blue is under, the optical illusion is a black line.
If the blue follows the red or the inverse at the horizontal in a neutral background(grey), the optical illusion, it’ll be a line between the blue and the red, of the same color than the background(grey).To observe this phenomenon, you need to use the picture in fullsize and to be at a distance of your screen.I’ve tested it with other backrgound colors and i’ve obtained the same results.
Finally i conclude that when the red is on the top of the blue, the line will be black and when it’s under, the line will be white. Another thing that i’ve noticed, it’s when the red is at the left of the blue, the line will be dark, but if the red is at the right of the blue, the line will be white.