First, you can't define red and blue because the wavelength spectrum is a continuum with no boundaries between the "colors", and second, what you are perceiving is the wavelength (or to be more precise, the combination of wavelengths) of the incoming light, not the color. Also, other species can see portions of the spectrum that we can't. In other words, color is a mental construction, red and blue exist only in our brains, the physical reality does not include such thing as color.