[Jimbee (OP)]

There is a story in the US. Fire engines are painted red so that they are more visible from a distance. Taxicabs are painted yellow for the same reason.

Why are red and yellow the most visible, or catchy to the eye, from a distance? Red and yellow have the lowest wave length on the visible spectrum. Is this something to do with optics and physics? Or is it just the human brain, maybe human psychology even?

Violet is at the other end of the spectrum. Shouldn't it be the most visible?

[vhfpmr]

Red is the longest wavelength, lowest frequency, violet the shortest wavelength highest frequency. The peak in the spectrum of sunlight is green, in the middle of the visible spectrum, so green is the colour that the human eye is the most sensitive to. The eye is also quite sensitive to yellow, which is next to green on the spectrum. I assume red has always been associated with danger because blood is red.

[alancalverd]

The father of a sometime girlfriend invented Coventry Fire Engine Yellow, demonstrably the most visible color in daylight or street lighting. It is a disgusting and distinctive blend of yellow and green.

Not that Coventry fire trucks were ever dirty before a job, but the problem with grubby green is that, as the army well knows, it is indistinguishable from fog, trees and grass, and dirty red doesn't stand out in a Midland townscape. CFEY leaps out at you under sodium street lighting or rural moonlight and is also used for NHS ambulances. Police, on the other hand, find the appearance of a white car or van with stripes or checkers often reduces the temperature of a fight before they make actual contact.

The blue end of the spectrum is strongly scattered by mist and fog, so blue-grey is favored by naval and air forces.  Their land vehicles are usually camouflage green but to avoid collisions they tend to have a CFEY or fluorescent yellow stripe at eye level.

[Petrochemicals]

Red is good for movement, the rods in your eyes are primarily there to sense for this, red for danger. Red traffic lights are noticeable. The cones in youre eyes use the other end of the spectrum and are more for detail.


Unsure why yellow is noticeable, other than by it's absence, its probably a group colour like everywhere else on year. Yellow is not a popular colour.

The father of a sometime girlfriend invented Coventry Fire Engine Yellow, demonstrably the most visible color in daylight or street lighting. It is a disgusting and distinctive blend of yellow and green

Airport fire engine green, tennis ball yellow, high viz coat, scientifically  proven to be the best colourfor your eyes. I don't know why, if you Google it let me know.

[alancalverd]

Yellow/blue contrast is preferred for safety rails and escape stairs because red-green color blindness is the most common and folk with poor overall visual sensitivity often find black/white contrast poor or can't see the black at all. Yellow seems to be the color least likely not to be discriminated against a contrasting background.

[Petrochemicals]

Yellow/blue contrast is preferred for safety rails and escape stairs because red-green color blindness is the most common and folk with poor overall visual sensitivity often find black/white contrast poor or can't see the black at all. Yellow seems to be the color least likely not to be discriminated against a contrasting background.

Amazingly tennis balls are yellow and used to be white at Wimbledon, yellow against a yellow green background doesn't seem to contrast but they work quite well. One would have thought pink would have been best, (but not on clay)