I recently noticed that it is hard to focus on blue light sources, especially at night. When observing a blue light source, e.g. a neon sign, it looks somewhat blurry. A sign with a different colour right beside it looks sharp.
I already know about the three kinds of cone cells in the human eye (I'm not a biologist) with their spectral sensitivity peaks in in short (S, 420–440 nm), middle (M, 530–540 nm), and long (L, 560–580 nm) light wavelengths . But does the spectral sensitivity correlate with focus? Or does our eye lens refract blue light in a different way?
When I screw up my eyes looking at a blue light, it becomes less blurry, but then all the other colours are blurred.