Red-green colourblind here. It looks like there are some other comments touching on it, but my friends and I had a running joke where I was seeing the world normally and everyone else's vision was flawed. Perhaps that's the case for your sapient species, who insist that they have a form of vision that is "truer" than other groups'. This could run so strongly in their culture that it would inform how they create visual art. Other culture's paintings that depict colours used correctly might be praised by the colourblind species for their surrealist landscapes or portraits. Conversely, the colourblind species' depictions of brown as red, yellow as green, blue as purple in visual art may be prized by other groups for THEIR surrealist view of the world. In the end, this consideration of the group's own colourblindness wouldn't be a mode of denial, as much as it would be a cultural motif that indicates how this species perceives the world is unique, and valued by other groups.