Red-violet
It has been reported by ophthalmologists that those who have their lenses removed and replaced with clear plastic intraocular lenses can see partway into the ultraviolet and view electric purple (a tone of red-violet) on the spectrum beyond Violet because it has been shown that the retina has some ultraviolet sensitivity which is normally blocked by the natural lens. Presumably, tetrachromatic animals such as birds can also see this color on the spectrum. These observers able to see partially into the ultraviolet describe the color they can see beyond violet in the ultraviolet as a sort of lilac, that is, a reddish-violet (purple) color that is the color of the lilac flower. (Presumably this color that they see would be electric purple, since electric purple is a pure chroma on the color wheel and would presumably be the color we would see on the spectrum beyond violet if we could see into the ultraviolet.)