Ultraviolet is outside of the visible spectrum. It isn't a color cause you can't see it. (Same for "infrared" on the other end of the spectrum.)
Purple is normally a darker color than violet.
Here is more than you probably want to know about purple:
Purple - Wikipedia, the free encyclopedia
Violet is a spectral color (approximately 380–420 nm), of a shorter wavelength than blue, while purple is a combination of red and blue or violet light. The purples are colors that are not spectral colors – purples are extra-spectral colors. In fact, purple was not present on Newton's color wheel (which went directly from violet to red), though it is on modern ones, between red and violet. There is no such thing as the "wavelength of purple light"; it only exists as a combination.
- For Teachers