I've been growing "Titan" sunflower seeds for about 6 years now. They result in large white/grey seeds. Last year some of my Titan plant heads were cross pollinated and came up with black seeds. When I planted those black seeds this spring these purple seeds resulted. The purple was pretty intense. It even stained my fingers.

I was harvesting the seed heads early because the squirrels (and birds) had taken more than half of them. I could see the local squirrel was very upset by my audacity to take any of the seeds for myself. It stared at me the entire time alarm calling and flicking it's tail.