"I has been misunderstood by writers, who have imagined that the peculiar individuals having this trait actually see the color on the letter, which is not the fact. It is a mental association, not a false vision." (Cytowic and Eagleman)
I have an issue with this quote, while I certainly agree with it, it disregards the possibility of projector synesthetes. While associators perceive colours or other stimuli in their "mind'd eye", projectors physically see graphemes transform colour. For instance, a "2" printed in black on white paper will appear to them as green. They have full knowledge that the 2 is printed in green, but they see green externally.
Cytowic, Richard E, and David Eagleman. Wednesday Is Indigo Blue. Cambridge, Mass.: MIT Press, 2009. Print.