Another vote for flax. I believe they do come in a variety of shades. I grow red flax, so if you get both red and blue flax, then to find a purple tinged one is not so unusual.
Nature does not hurry, yet everything is accomplished – Lao Tzu
Well- it seems that this is actually a “purple oleander”.
I’ve been away for a bit with a lovely lady looking after my two Burmese boys. She assures me that this is a purple oleander ( and she’s pretty knowledgeable plant wise). I’ve looked it up and I’m inclined to agree.
However - VERY toxic for humans and little cats!