A designer chair by Winchester business Kristen Rivoli Interior Design is currently on display as part of a travelling exhibition beginning in Natick.Rivoli’s chair, “Purple Reign,” began as a simple armchair in an outdated floral design before being reupholstered with a purple fabric.For the exhibit, titled “Take a Seat,” industry professionals and students transform existing chairs into one-of-a-kind pieces that are eventually auctioned for charity.