For as long as I can remember, I have associated different numbers with specific colors. Although the given colors have occasionally changed over time, most of the numbers have always had a distinct color associated with them.

“The number 4 is red …”

My name is Rainer, and I am a grapheme→color synesthete.

Scientifically, synesthesia is a neurologically based phenomenon in which stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway. In grapheme→color synesthesia, letters and/or numbers are perceived as inherently colored. For me, numbers by far have the strongest color associations, while letters and other symbols have come and gone in the past.

The intensity of the colors has varied over the years. There have been times when a given number has not actively been linked to a specific color. Sometimes two numbers have swapped colors. One thing has always remained the same, however. The number 4 is red. Likewise, the numbers 6, 7, 8, and 9 have always been orange, brown, gray, and black, respectively. This may sound absolutely crazy to someone who is not a synesthete themselves, so let me try to explain.

When I see a number in print, I do not necessarily see it in color. I still see it in whatever color it is printed.


The printed number above is, when I look at the screen, black. However, to me, the number itself is red, regardless of printed color. Make sense?

This experience is completely automatic and involuntary.

In fact, growing up, I was completely unaware that others did not experience letters and numbers the same way. To a non-synesthete, this sensory experience may seem like complete fiction. Let me assure you that it is very real. It is not like I sat down one day and decided to associate the different letters and numbers with certain colors. They have always been colored. I can no more explain this sensory “phenomenon” than I could attempt to explain to a deaf person what music “sounds” like. The synesthesia itself is just as natural to me as sounds are to a hearing person.

If a person were to walk up to you and ask what color the sky is, the natural answer would be “blue”. That is just how it is. The sky is blue.

Now, if someone walked up to you and asked what color the number 8 is, you might respond with a blank stare … that is, unless you are a synesthete. Were someone to ask me that question, my immediate response would be “gray”. That is just how it is. The number 8 is gray.

Although certain color associations are more common than others, no two synesthetes share the exact same sensory experience. For example, the letter “A” is most commonly perceived as being red. I, too, share this commonality.

Color-Grapheme Synesthesia

The image above shows what color the numbers are to me. It is interesting to note that not only is the number 5 “green” … it is a specific shade of green. In fact, it was extremely difficult to provide an accurate representation in the image above.

The reports and experiences vary greatly from one synesthete to another.

“I came back from college on a semester break, and was sitting with my family around the dinner table, and — I don’t know why I said it, but — I said, ‘The number five is yellow.’ There was a pause, and my father said, ‘No, it’s yellow-ochre.’ And my mother and my brother looked at us like, ‘this is a new game, would you share the rules with us?’ And I was dumbfounded. […] At that time in my life I was having trouble deciding whether the number two was green and the number six blue, or just the other way around. And I said to my father, ‘Is the number two green?’ and he said, ‘Yes, definitely. It’s green.’ And then he took a long look at my mother and my brother and became very quiet. Thirty years after that, he came to my loft in Manhattan and he said, ‘you know, the number four is red, and the number zero is white. And,’ he said, ‘the number nine is green.’ I said, ‘Well, I agree with you about the four and the zero, but nine is definitely not green!’

Nobel prize winning physicist, Robert Feynman, once said:

“When I see equations, I see the letters in colors. I don’t know why. As I’m talking, I see vague pictures of Bessel functions from Jahnke and Emde’s book, with light-tan j’s, slightly violet-bluish n’s, and dark brown x’s flying around. And I wonder what the hell it must look like to the students.”

Writer Patricia Lynne Duffy explains her own experience like this:

“One day I realized that to make an ‘R’ all I had to do was first write a ‘P’ and then draw a line down from its loop. And I was so surprised that I could turn a yellow letter into an orange letter just by adding a line.”

While some actually see the letters and numbers in color, I, and many synesthetes with me, have no problem separating the “external” from the “internal” color of each symbol. There is a difference between real-world color and my sensory color associations. A fellow synesthete referred to this when she said:

“It is difficult to explain … I see what you see. I know the numbers are in black … but as soon as I recognise the form of a 7 it has to be yellow.”

These sensations are not at all bothersome or problematic. To me, this is absolutely normal and natural. In fact, I cannot even imagine a world where 4’s are not red.

Have you had synesthetic experiences of your own?

“The color of truth is gray.”
André Gide (1869–1951)