If the inability to differentiate blue and black and brown is caused by the gradual yellowing of the lens in our eyes, would wearing another color lens make it possible to see the colors?
The yellowing of our lens with age does contribute to our inability to distinguish black, blue, and brown in dim lighting, but the dim lighting is probably a bigger factor. The yellowing of our lens means that less blue light gets through to our retinas, but dim incandescent bulbs also contain very little blue light. The lack of blue light to respond to is what causes these particular difficulties with dark colors. Unfortunately it can´t be fixed with a filter. Another filter would just take away more light and, even if that light was of a different color than blue, less light makes it even harder to distinguish colors. The best answer is to look at the colors (typically socks!) under brighter light and, if possible, bluer light such as natural daylight.
