Cute Young Blonde Girl Reveals In Purple Stockings

In color theory, a "purple" is defined as any non-spectral color between violet and red (excluding violet and red themselves). The spectral colors violet and indigo are not purples according to color theory but they are purples according to common English usage since they are between red and blue.
In art, purple is the color on the color wheel between magenta and violet and its tints and shades.
In human color psychology, purple is also associated with royalty and nobility (stemming from classical antiquity when Tyrian purple was only affordable to the elites).