> Simple layman's explanation (from a layman): lenses spread light out a bit as the light passes through, so the red wavelengths hit the sensor in a slightly di

> Simple layman's explanation (from a layman): lenses spread light out a bit as the light passes through, so the red wavelengths hit the sensor in a slightly different spot than the blue wavelengths. What you've described is chromatic aberration. Diffraction refers to the spreading of waves around an obstacle -- such as the aperture blades in your camera. No lens need be involved -- you can get diffraction with a pinhole camera.