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What numbers are blue?

Numbers can evoke different colors and sensations for people based on their experiences and associations. While there are no universally agreed upon “blue” numbers, some numbers may be more likely to be perceived as blue by certain individuals or cultures. In this article, we’ll explore some theories around why certain numbers may be seen as blue and look at examples of numbers that tend to evoke blue hues.

The Psychology of Number-Color Associations

Humans are wired to search for patterns and meaning. This drive applies to numbers as well. Throughout history, humans have tried to map numbers and numeric concepts to colors, sounds, personalities and more. While not everyone sees numbers in color, the phenomenon, often called number-color synesthesia, is real for some.

Research suggests number-color associations may be driven by the following factors:

  • Inherent properties of numbers: Lower numbers may map to darker colors while higher numbers go with lighter hues. The numeral shapes and angles may also play a role.
  • Learned associations: Associating certain numbers with colors due to toys, refrigerator magnets, etc. during childhood.
  • Cultural influences: Colors assigned to numbers vary across cultures. Chinese and Korean cultures tend to associate red with luck and fortune.
  • Personal experiences: Important numbers in someone’s life may be strongly tied to specific colors.
  • Mnemonic connections: Rhyming patterns and other memory techniques may link certain numbers to colors.

While the causes are debatable, number-color synesthesia is real for some. When it comes to blue numbers, let’s look at some patterns that may explain why they stand out.

Cool, Calming Blue

Blue is widely considered the world’s most popular color. Surveys show both men and women are most likely to say blue is their favorite color.

Some symbolic associations with the color blue include:

  • Stability and depth
  • Wisdom, confidence and intelligence
  • Tranquility and calmness
  • Trust, loyalty and integrity
  • Cleanliness and purity

With these attributes, it makes sense that people may be more likely to associate certain numbers with the color blue. let’s look at some examples.

Single Digit Blues: 4, 6 and 9

Among the single digit numbers, 4, 6 and 9 tend to most commonly associate with the color blue according to surveys. Some possible reasons:

  • 4 – The numeral 4 has sharp angles pointing down like an “arrowhead” which may evoke the feeling of descent. Blue evokes depth.
  • 6 – The curves of the numeral 6 may feel “fluid” like waves of water. Blue calls to mind bodies of water.
  • 9 – Upside down, 9 looks like a balloon or bubble floating upward. Blue conveys lightness and air.

Here is a table summarizing some single digit numbers and their most commonly associated colors:

Number Most Common Color Association
0 White
1 White, gold
2 Red
3 Yellow
4 Blue
5 Red
6 Blue
7 Green, purple
8 Red, purple
9 Blue

The Blues of Milestone Ages

When it comes to milestone ages, the numbers 0, 10, 13, 18, 21, 30, 40, 50, and 100 tend to most commonly associate with blue hues.

Let’s explore why some of these ages may feel “blue”:

  • 10 – Entering the double digits feels like a major life step. Blue represents stability.
  • 13 – The onset of the teenage years brings new depths of emotion. Blue conveys inner complexity.
  • 18 – Legal adulthood brings serious responsibilities. Blue feels mature and thoughtful.
  • 21 – In the US, turning 21 enables new freedoms. Blue implies freedom’s calm confidence.
  • 30 – This new decade feels like a transition into true adulthood. Blue reflects wisdom and clarity.

Here’s a table of milestone ages and their most associated colors:

Age Most Common Color Association
0 White
10 Blue
13 Blue
16 Red
18 Blue
21 Blue
30 Blue
40 Blue
50 Blue
100 Blue

“Clean” Numbers

Numbers like 7, 10 and its multiples like 20, 30, 100 etc. tend to feel “clean” and “whole” to many people. This perception of purity may link them to blue.

7 has mythological significance in many cultures as a prime number. It feels unique and indivisible. 10 is the base of our numerical system. Its wholeness resonates. Multiples of 10 feel complete as well.

Blue is the color of cleanliness, clarity, and precision. It makes sense that stereotypically neat, tidy numbers would correlate with blue hues.

Calm and Relaxing Numbers

Just as blue evokes calm, certain numbers may trigger a sense of relaxation, comfort or stillness. These include:

  • 0 – The lack of value can feel tranquil and empty like the sky or sea.
  • 2 – Its symmetry and repetition feel harmonious and still.
  • 11 – Identical digits side by side mirror each other like calm waters.
  • 44 – The repetition creates a zen-like pattern.

Blue’s ability to soothe emotions may cause people to associate it with numbers that induce calm or relaxation. The tranquility of blue resonates with the feelings these numbers evoke.

Cultural and Idiomatic Associations

Language and culture also influence number-color perceptions. Some examples of blue numbers from idioms and cultural contexts include:

  • The “big blue” – Meaning the sea or ocean
  • “Feeling blue” – Sadness or melancholy
  • “Blue Monday” – Symbolizing depression and the start of a workweek
  • “Blue moon” – A rare event, relating rarity to the color
  • China – 4 is considered unlucky because “four” sounds like the word for “death.”

These expressions link blue to emotions ranging from sadness to serenity. People surrounded by this cultural imagery may be predisposed to view certain numbers as blue.

Personal Experiences and Memories

As with colors, numbers may remind someone of specific events, people or periods in their life. Past experiences can strongly shape number-color associations. Some examples include:

  • Jersey numbers of favorite athletes and teams
  • Colors of childhood toys like blocks or flashcards
  • Colors used to teach numbers in school
  • Colors of a memorable cake on a birthday
  • Hues associated with past homes’ addresses

Positive memories and experiences involving certain numbers may link them to favored colors like blue. Nostalgia and emotion can be powerful drivers of number perceptions.


While not universal, patterns exist around why certain numbers may feel intrinsically “blue” to people. Numerals’ shapes, cleanliness, cultural associations and personal experiences can all unconsciously cause numbers to elicit blue hues.

Does 5 make you think of red or 10 fill you with a calm, sky blue? Number-color perceptions are deeply personal. But exploring popular associations gives insight into how humans search for meaning in abstract symbols like numbers.

Numbers aren’t just numerical values. They take on colors, textures and emotions in our minds. So for some people, 4, 6 and 9 will always be shades of blue – the coolest numbers of all.