There are some shades/ colours which always elude us. Navy & I were debating what distinguishes a violet from a purple. Well we both know the textbook definition- " when mixing paint, violet is equal parts red and blue, whereas purple has higher saturations of blue" One is named after the dye that comes from a sea-creature (purpura) and the other is named after the flower.
Here is an interesting link on violets (the flower) which does not always stay true to its colour ( pun intended)- the state flower of Illinois is the Purple Violet!!