Chromostereopsis

Chromostereopsis is a depth illusion where intense warm vs. cool colors appear to sit on different planes relative to the viewer. 

In the illusion above, it appears to my eye that the red is a little lower or farther away. But others report the opposite effect, and some people don't see any depth illusion. 

Mindhacks explains that "red and blue are at opposite ends of the light spectrum," and as a result, "different wavelengths of light will be focussed differently on the back of the eyes. This may also be why some people report that their glasses intensify the effect."

More at Mindhacks

Thanks, Ron Harris