Question regarding tunnels between Drayton Park & Moorgate

The opsins in the human eye (in the "cone" cells of the retina) are most sensitive to light of 534–545 nm and 564–580 nm (middle and long wave respectively, aka "green" and "red"). These are the most common receptor types in the retina, and lamps of a yellow/orange hue are therefore most effective at stimulating the photopic visual system. By contrast the scotopic or "night-vision" system is connected to "rod" cells filled with rhodopsin which peaks at around 500nm ("bluey-green") but which is "bleached out" at all but low levels of illumination. The "blue" cones peak at around 420nm.
As mentioned above, tungsten light from a heated filament contains a preponderance of longer wavelengths and is thus more effective at stimulating the eye's photoreceptors. This is why I prefer the orange glow of sodium street lights over the newer LED broad spectrum ones. The blue component of LEDS bleaches out the rhodopsin and makes transition from day to night vision much more lengthy, whereas with the sodium lamps you are operating mostly in the mesoscopic range (where both rods and cones are operating at the same time). An interesting experiment with mesoscopic vision is to take a walk along a shoreline where there is a pier in the distance - at a great distance, the light on the end of the pier will be grey/white or twinkly blue; as you get closer and more photons are received by the eye, then you will begin to resolve a yellowish tinge to the light; move closer still and the photons will be being captured by more than a small selection of cones and the red and green lights will resolve so you can see both colours.
Can you tell that the visual system is my "thang"?
Anyway, the primate visual system has a feature dubbed "colour constancy", that is to say that broad categories of colour remain the same under widely varying illumination conditions; a leaf in summer is green at dawn, midday and dusk, under cloudy skies or in bright sunlight. The shade or hue may vary, but it still appears green. You can set up illumination conditions where a green surface reflects more "red" light than "green", and it still appears green providing the same illumination falls on a range of other differently coloured surfaces. Take away the other surfaces, and the green patch becomes red.
This "computation" of colour is thought to occur in the both the eye and the brain according to the Retinex theory of Edwin Land, inventor and founder of Polaroid; so he knew a thing or two about colour photography!
Film, of course, doesn't have a brain, so different chemistries were created for different standard illuminants - tungsten, daylight, fluorescent etc. A set of colour balancing filters which go on the lens allowed film types to be used in conditions other than the one they were formulated for, e.g. an 80A filter allows daylight film to be used indoors under tungsten light. Flash guns were formulated to produce an illumination similar to daylight.

Digital cameras do have a brain, and they can correct the image to compensate for the illuminant. The camera assumes a standard illuminant based on the old film standards, but can create a colour calibration setting of their own by using a "grey 20" or other surface which is neutral (a sheet of white A4, for example). You can over-ride the automatic calculation of the illuminant, but doing so could result in a colour cast if you change lighting without changing the setting.

You can read more <a href="http://www.webexhibits.org/causesofcolor/1G.html">here.</a> This site is actually an accurate description of how colour vision works. There are many, many, many sites which are, frankly, total bunkum.