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It is often claimed that yellow (or a particular hue of yellow or yellow-green) is the most conspicuous color. This supposed fact is used in many industries from safety to advertising. This reasoning is used as justification for the yellow coloration of everything from safety vests to school buses to hard hats.

Yellow safety vest

You can see this claim made here:

Recent research in commercial and safety fields has converged on the same conclusion: the most conspicuous colors are yellow and yellow-green, sometimes called "lime yellow."

And here:

Lateral peripheral vision for detecting yellows is 1.24 times greater than for red.

Many experts also point out that colors such as yellow or greenish-yellow are more visible to the human eye under dimmer conditions compared to red.

While both sites mention "science", "experts", or "studies", there are no direct references or links provided. The first site has references, but they are to secondary works and not the studies themselves--with the exception of a 1931 study for which that site is the only reference in Google search results.

Conversely, I have seen some claims that other colors such as red, orange, or pink are more conspicuous than yellow.

One argument is that during the daytime yellow is more likely to blend into background colors.

So be careful to take into account not only colors' "raw" visibility but also the ability to discern them from background.

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    Maybe this ambulancevisibility.com/index.php?p=1_16 can lead to an answer.
    – GEdgar
    Oct 26, 2015 at 20:45
  • The bit about yellow is better for peripheral vision seems strange, considering yellow is Red and Green, and you find less of them towards the edge (more blue).
    – Tim
    Oct 26, 2015 at 23:02
  • A study about on-water visibility concludes that fluorescent green, followed by fluorescent orange, were the most conspicuous colors for a floating target when compared to nonfluorescent red and non-fluorescent yellow.
    – ermanen
    Nov 17, 2015 at 15:44
  • @ermanen This seems to not take into account the large distances tested in the Navy study in cobaltduck's answer, but otherwise this is definitely interesting. It seems that there are several factors involved in detectability that may make generic ranking difficult.
    – called2voyage
    Nov 17, 2015 at 15:55
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    A personal observation serves as a counterexample: when I first saw some yellow-green color for some hazard indication I noticed how invisible it was against bright Dallas concrete. context matters so one cannot answer “yes” unqualified. There is no most conspicuous color, since it depends on the surroundings.
    – JDługosz
    Nov 3, 2016 at 14:50

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I recalled hearing that the U.S. Coast Guard had studied this, in an effort to determine the best colors for life rafts, to make them more likely to be seen by the spotters aboard SAR aircraft. I could not find that study, but I did find a similar, older one by the U.S. Navy.

I did not feel like reading the whole thing, so I skipped to the conclusion on page 57:

  1. Fluorescent paints, particularly the yellow-orange and red orange, are superior in detectability to ordinary paints.

  2. Of the ordinary paints tested, the most conspicuous colors were those of high saturation and/or brightness.

This paper does mention a color called "Saturn Yellow" elsewhere as having superior detection. It also indicates brightness (florescence) may be more important than hue, as the observers were often unable to correctly report the color of an object from a great distance.

The conclusion seems to favor orange, and the fact that PFDs (life jackets) and life rafts today are often orange is also compelling.

EDIT: As a counter point, I have discovered that the International Tennis Federation had done its own study in the 1970s, with emphasis on television viewers. I couldn't confirm it, but it appears they did not release the full study publicly, only the conclusion. They were even asked "Why not pink or orange?" and only said the study indicated yellow was best.

My original intent was that the answer to the stated question is "no." But when we put the Navy and ITF data together with the ideas discussed in the comments, perhaps the best answer one can give is just "Maybe, it depends."

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    I found this bit in that study most interesting: "Yellow test objects, particularly on a blue ground, are found to appear white when they are a long distance away. The dinghies, having apparently become white in colour, could easily be mis-taken for a collection of seabirds, or even flecks of foam. When other colours were tested it was soon found that the best one of all is a bright orange-red. This keeps its colour far better than yellow when seen at a distance, and renders objects easily distinguishable."
    – called2voyage
    Oct 27, 2015 at 18:12
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    It is interesting that yellow does seem to be superior in conspicuity if long distances are not taken into account, but the possibility of yellow being mistaken for background seems to be a major hit in any environment.
    – called2voyage
    Oct 27, 2015 at 18:23
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    I should also point out that what is important to the Navy and Coast Guard (visibility by a spotter in an aircraft against a background of ocean waves) is different from what is important to a construction worker (visibility by a motorist against a background of concrete or asphalt and other cars). These environmental differences could change the results.
    – cobaltduck
    Oct 27, 2015 at 18:25
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    Yes, that is a point I've taken into consideration. There are two factors: 1) discernability from white (this seems to be a potential factor in many environments) and 2) discernability at a great distance (this seems perhaps less important in the urban environment, which may be why yellow-greens are acceptable alternatives to more orange colors).
    – called2voyage
    Oct 27, 2015 at 18:27
  • Would the down-voter care to explain, please?
    – cobaltduck
    Nov 16, 2015 at 17:22

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