We see it often enough. Red eyed monsters, ghosts, robots, etc. Media monsters are made to be creepy and unsettling generally. So there must be a bases for them to have this trait.

I know red has a natural psychological effect, it grabs attention quite easily. So would it benefit a creature who's purpose was to terrorize, or otherwise frighten the enemy or prey?

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    $\begingroup$ This question might help you: Is there any plausible reason for a robots eyes to glow?. And if you are only interested in designing a creature you should edit your title to leave out the robot. $\endgroup$
    – Secespitus
    Apr 20, 2017 at 9:34
  • $\begingroup$ @Secespitus I took a good look at other topics before I posted. Thank you however. My mean reason for asking is because I find it interesting and I figured the question could help others. I'm also asking about the general color of the eyes themselves and the psychological effects that could have on its prey, or target. So glowing or not never mattered in that respect $\endgroup$ Apr 20, 2017 at 9:42
  • $\begingroup$ In animals red eyes are generally the result of having no coloration in the eyes themselves, so the red blood vessels create the coloring > red. As for terrifying, scaring another animal tends to be a defensive measure. To stop a predator from attacking. In that way red is used to signal that you're poisonous > frogs. $\endgroup$
    – Mormacil
    Apr 20, 2017 at 9:44
  • $\begingroup$ @WarmShadow Here is a question about red eyes in humans with an example about frogs: How would red eyes occur in a human without underlying medical conditions?. Those frogs are a perfect example for your red eyed creature, as Mormacil has already said. $\endgroup$
    – Secespitus
    Apr 20, 2017 at 9:49
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    $\begingroup$ Just a hint: This question has, as of writing this, been viewed 29 times and was asked ~ 1 hour ago. Only a very small percentage of the people who are active here have seen your question. It is, of course, your decision to accept an answer if it is helpful to you, but normally it's a good idea to wait at least ~ 24 hours before accepting an answer, so that the regulars have seen your question. Someone could have other interesting ideas and accepting an answer can sometimes discourage other people from posting new answers. Just a hint for future questions. $\endgroup$
    – Secespitus
    Apr 20, 2017 at 10:47

2 Answers 2


There are several very precise reasons to design red into anything you want someone to be afraid of.

It's worth noting that a human seeing the color red experiences two interesting things: Increased heart rate and increased adrenaline flow. The increased blood flow is a reaction to our association with red and it's common social meanings. When people are angry or embarrassed, their faces may flush red. Given that these are both indications of negative social situations, we learn to associate deep red with negative contexts. Furthering this, red is the color of blood, and visible blood likely means injury of some sort has happened. Since our animal natures would rather avoid injury, blood-red colors tend to intimidate our sense of safety.

(Note: There are also positive contexts for red colors, as in sensual use or sport, but these are beyond the scope of a "creepy monster" situation.)

Consider also that red is the color of fire. Fire, as all prudent humans know, is dangerous to touch. At the very least, you'd want to be cautious when handling fire. However, when fire grows out of control, your tendency would be to run from it so as to avoid painful outcomes.

From the evolutionary perspective, many poisonous animals use red as a way to signify that they are dangerous. Many snakes, insects, and fruits use this tact to either directly demonstrate danger or imply danger. The animal inside all humans therefore sees red as a potentially poisonous color, and thus will try to avoid it in already negative contexts.

Physiologically, When you see red, your brain will examine the thing its attached to and, most likely, prepare your fight-or-flight response by increasing your heart rate and adrenaline levels.

On a purely physical level, this will lead to heightened emotions. Assuming you are currently a little freaked out - because whatever situation has put you in the direct gaze of a creepy being would freak you out - seeing red eyes will undoubtedly raise your hackles and cause some intense feelings, likely even outright fear.

There are many excellent reasons to use the color red in eyes for intimidation and fear purposes.


Yes. As the old saying/cliche goes: "The eyes are the gateway to the soul". As humans, we are programmed to make eye contact (fun fact: we are the only animals whose whites of the eyes are always visible).

Due to this eye "fixation", eyes are often used to communicate significant changes to the character e.g. pupils shrinking/expanding or the iris changing colour. We are also prone to noticing if something is "wrong" with the eye, like being bloodshot or if they are blind.

  • $\begingroup$ This answer seems pretty good to me. Gives enough logical reasoning for designing a creature with red colored eyes etc. The comments above were quite informative as well. $\endgroup$ Apr 20, 2017 at 10:05
  • $\begingroup$ What does any of this have to do with specifically red coloring in the eye? (Also, what species are you referring to? Because my sclera aren't always visible. In fact, they're only visible roughly 90% of the time.) $\endgroup$
    – Frostfyre
    Apr 20, 2017 at 12:58
  • $\begingroup$ @Frostfyre When are the whites not visible? Other than when the eyes are closed. $\endgroup$ Apr 20, 2017 at 13:07
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    $\begingroup$ @Frostfire: "Generally, between each blink is an interval of 2–10 seconds" (Wikipedia). Even allowing for 400 ms blink duration (which does seem excessive), blinking would count for 4% to 20% of the time. $\endgroup$
    – AlexP
    Apr 20, 2017 at 14:21
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    $\begingroup$ @AlexP Sorry, meant to say 10% is spent blinking. $\endgroup$
    – Frostfyre
    Apr 20, 2017 at 15:13

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