I have a couple of questions regarding color and the prevalence of disorders surrounding color eyesight.

I have been thinking about the issue of not seeing color at night. Is this because of the lack of photons stimulating the cones? Or is there possibly an inhibitor when the photoreceptors used for night vision are activated. It seems that there is a difference between not being activated and being inhibited.

Regarding seeing light at night. How are we so able to distinguish between red light and green light while driving in the evening if we need to adjust to the dark as we drive. It seems that at night, it takes no time at all to determine the color of a street light. Is the white light behind the colored screen instantly stimulating the cones in our eyes?

Disorders. I still am not clear on what color blindness is. The difference between red-green color blindness and other types of color blindness is very unclear (no pun intended). Is red-green color blindness the failure of our photoreceptors from absorbing shorter wave lengths or longer wave lengths of light. In class we talked about what wave lengths of light are absorbed, and the resulting color observed but I am still confused. Do our photoreceptors absorb the wavelengths we see, or the wavelengths that we don't see? I know this is a pretty fundamental point, but I want to be clear.

Clarity (pun intended) important. One doesn't see color in a dark forest at night because the intensity of light coming from all point sources is too low to activate cones. Yes, in principle it could be because cones (or something in the subsequent cone pathway) are inhibited, but in actuality the differing absolute light sensitivities of rods and cones provide an adequate explanation (at least to a first approximation) without invoking any inhibition. When driving in the dark along a city highway, the point sources of light which are street lights, signs, billboards, and so forth are of higher intensity, so they DO activate the cone system and one sees those parts of the night scene in color. That clearer? As for color blindness, the most common forms are two different versions of "red/green" color blindness. In one, the long wave length pigement is missing; in the other, it is the medium wave length pigment that is missing. Because the two pigments have largely overlapping absorption spectra, the consequences of missing either are pretty much the same: difficulty in discriminating wavelengths toward the long wave-length (red) end of the spectrum (wavelengths long enough so they are being absorbed by, pretty much, only one pigment, where normally they would be absorbed by two), hence confusing "reds and greens", both of which (as well as all intermediate hues) are seen as they same "color". Photoreceptors absorb the wavelengths we SEE; we infer the ones we don't see (ultraviolet, infrared, etc). See? PG