Violet and Purple are the same?
Essentially the same. But purpura is also used for purple.
Violet and purple look very similar; but violet is a true color, with its own wavelength on the spectrum of visible light, while purple is a composite color, made by combining blue and red. (from Wikipedia)
Oxford comma in Esperanto?
Fortunately, Esperanto punctuation is (often…) multinational-flexible! :D
mi parolas esperanton ekde kvin jaroj, kaj mi neniam estas audinta la vorton "violkolora"