are all I. pallida purple?

Some are white. They yellow appeared with I. variegata, which are red & yellow bicolors.

And some are towards blue.

Is there a common name? Why can't I find them for sale? Are they heritage iris?

Their common name is pallida. They are also called the Dalmation iris or sweet iris. They are heritage or historic irises. I know of no place where you can buy the straight pallida, but Superstition Iris sells a few of the crosses, including Princess Beatrice.

The striped leaved ones are more common, pallida variegata. Also goes by pallida albo marginata, and pallida argentea variegata, and some other names. They come in a white and green striped leave, and a cream and green striped leave, also. The leaves on the striped ones are lovely all season long.

They are listed on Wikipedia.

Here's some more info:

http://www.hort.wisc.edu/mastergardener/Features/flowers/Iris_pallida/Iris_pallida.htm


http://www.highcountrygardens.com/catalog/product/61007/

Thx.