Detail of purple Queen Anne's lace

I have no idea what causes the purple variation -- there are other specimens around here and they're all the normal white with tiny purple flower at the center of the flower head (except for one, in which the tiny central flower is more maroon). Queen Anne's lace is also known as wild carrot, and the roots are edible when they're young. It's my hope to collect the seeds of this one -- I wonder if the variation is genetic or environmental.