I don't know if your growing season is long enough for sweet potatoes but they are very easy to start and grow. I have been growing the "same" sweets for many years, just sprouting the last ones from storage around January and planting them out in late May. You have a heated greenhouse I think? Maybe you could try starting them in there and then putting them out in the garden? I never saw purple leaves on edible sweets (I wonder if ALL are edible, even those very fancy-leaved ones?). One year I grew white fleshed red skinned sweets but they were not as good as old-fashioned orange ones.

I have a cat named Peach!

My Peaches kitty is what they call a muted calico. She is gray with splotches of yellow and has the usual white cat trimmings.

My Peach is a yellow tabby, missing one eye with a bent ear. He's the sweetest little guy.