Final answer:
Grapheme Colour Synaesthesia is a condition in which individuals automatically associate specific colors with particular letters or numbers. It's an involuntary perceptual experience distinguishing certain graphemes with a consistent color, unlike visual illusions explained by opponent process theory or sensory recognition like graphesthesia.
Step-by-step explanation:
An example of Grapheme Colour Synaesthesia involves individuals associating specific letters or numbers with particular colors. For instance, someone with this form of synesthesia might perceive the letter 'A' as red or the number '2' as blue consistently. This unique sensory experience creates a vivid and automatic connection between the visual representation of graphemes and a palette of colors. This phenomenon is not an artistic choice, like a painter attracting attention with vibrant hues; it is an involuntary perceptual condition.
Synesthesia is not to be confused with the effects of the opponent process theory, which explains a 'trick' on the retina and brain about the colors one is observing in the visual field. Nor should it be mistaken for graphesthesia, which is the ability to recognize writing on the skin purely by the sensation of touch. Both are different phenomena related to the perception of stimuli.