Subsequent large-scale studies have suggested that the prevalence of synesthesia might be as high as 1 in 20 across all forms and 1 in 100 for grapheme-color synesthesia (J. Simner, personal communication).

Our own informal samples have suggested that the prevalence of grapheme-color synesthesia might be between 1 in 200 (Ramachandran and Hubbard, 2001b) and 1 in 100 (Mulvenna et al., 2004).

Grapheme–color synesthesia: Letters or numbers are seen to have colors of their own.

GRAPHEME, OR COLOR, SYNESTHESIA: Letters or numbers are perceived as inherently colored.

Subsequent large-scale studies have suggested that the prevalence of synesthesia might be as high as 1 in 20 across all forms and 1 in 100 for grapheme-color synesthesia (J. Simner, personal communication).

By far the most common type of synesthesia, affecting more than 60 percent of synesthetes, grapheme-color is a condition in which letters of the alphabet or numbers have a distinct color to them.

Colour-grapheme synesthesia – colours are associated with numbers, words or letters

Our own informal samples have suggested that the prevalence of grapheme-color synesthesia might be between 1 in 200 (Ramachandran and Hubbard, 2001b) and 1 in 100 (Mulvenna et al., 2004).

Colored days of the week and colored graphemes are the most common types.

In typography, a grapheme is the fundamental unit in written language.

If it's between tone and color, you get tone-color synesthesia.

Synesthesia has been used as a counter-example to color objectivism.

Synesthesia: do you have sensorial associations with shape, colour, scent, and sound?

SYNAESTHESIA: What is the taste of the color blue?

Synaesthesia: What is the taste of the color blue?