The local Kinko's copy services displays its name in blue light on the sign outside. Just like every other blue light sign I've seen over the years, it is blurry. This can't be because of my aging eyes, since I remember them looking blurry 20 years ago.

Red light doesn't conflict with the eye's 'dark adaptation' as much as other frequencies, which is why we used a red night light for the baby's room. We could see what we were doing, without blindly stubbing toes on the way back to bed later. If blue light strongly reduces the 'dark adaptation' of the eye, then natural jitter of the eye, by moving the image around on the back of the eye, will create a desensitized zone where the image of the blue light lands. The blue sign isn't intensely bright, so it relies on contrast with the dark to create its effect--but that contrast has been partly destroyed, and so the image is not sharp, which I see as blur.

Maybe, maybe not, but it seems plausible.