Regional usage of "Violet" and "Purple"
Here in the U.S., I think most speakers would almost always use purple.
Why? For one, there is a flower called a violet, so folks are less likely to describe a different flower as violet. The Ngram below supports my claim:
For another, when describing just about any object of that color, I think most people (except perhaps physicists) use purple in conversation, rather than violet (although the it's not like the latter is never used).