General:
* Purple
* Violet
* Lavender
* Lilac
More Specific:
* Amethyst (deep, purplish-blue)
* Mauve (pale, grayish-purple)
* Plum (deep, reddish-purple)
* Orchid (light, pinkish-purple)
* Indigo (dark, bluish-purple)
* Magenta (bright, reddish-purple)
* Lavender blue (light, bluish-purple)
* Royal purple (rich, deep purple)
* Heather (light, grayish-purple)
* Wisteria (pale, bluish-purple)
Figurative:
* Royal
* Luxurious
* Mystical
* Spiritual
* Elegant
* Regal
* Mysterious
* Enigmatic
* Dreamy
* Nostalgic
The best words to describe purple depend on the specific shade you're talking about and the context.