Color ontology is the philosophical study of the nature of color. Synesthesia is a neurological condition in which the stimulation of one sensory modality or cognitive pathway leads involuntarily to experiences in a second modality or cognitive pathway. Synesthetic colors are thus colors reliably induced by non-visual stimuli. Currently, there is no philosophical theory of color that explicitly addresses synesthetic color. This omission raises three questions which underlie this thesis. How would the main theories in color ontology interpret synesthetic colors? Which, if any, of these theories would be able to treat synesthetic color as being more than misperception? What would be the costs of adopting such a theory? In Part I, I introduce and discuss four prominent theories of color: physicalism (chapter 1), eliminativism (chapter 2), role functionalism (chapter 3), and sensory classificationism (chapter 4). In Part II, I introduce perceptual pragmatism as an alternative to these views. Perceptual pragmatism consists in the defence of two main theses: (i) that colors are properties of interactions between a color perceiver and an external stimulus that induces color experience, and (ii) that perceptual states are correct insofar as they are useful to the perceiving organism. In chapter 5, I defend the first thesis. In chapter 6, I defend the second thesis. In chapter 7, I assess each theory’s ability to account for synesthetic color. In chapter 8, I address the common sense objection that colors do not look like properties of events. In conclusion, I find perceptual pragmatism to be the only theory capable of offering a satisfactory account of synesthetic color. However, it is also the theory most at odds with common sense. I conclude that if we want a theory that can account for the uncommon colors of synesthesia, we must reject the common sense view of color. / Thesis / Master of Arts (MA) / Color ontology is the philosophical study of the nature of color. Synesthesia is a neurological condition in which the stimulation of one sensory modality or cognitive pathway leads involuntarily to experiences in a second modality or cognitive pathway. Synesthetic colors are thus colors reliably induced by non-visual stimuli. As it stands, there is no philosophical theory of color that explicitly addresses synesthetic color. Of the current theories in color ontology I argue that only one—perceptual pragmatism—is able to offer a satisfactory account of synesthetic color. However, perceptual pragmatism is also the theory most at odds with common sense. I conclude that if we want a theory that can account for the uncommon colors of synesthesia, we must be willing to reject the common sense view of color.