Last year I purchased an ornamental sweet potato vine from a local store. The leaves of the vine were a beautiful silvery and lavender/purple shade. At the end of the season, while pulling the vine up from the planter, I discovered a sweet potato, which I saved and have sprouted on my kitchen windowsill. I have pinched off the tips of the vines, rooted and planted slips from this sweet potato in containers all over my yard. My question is this: Why are my plants not the lovely silvery lavender/purple colored leaves that the parent plant was last year?

That's odd. It seems they would be just like the parent plant. Are the new plants getting too much sun. Ornamental sweet potatoes always have their best color in the shade.