After opening its first Colorado store in Boulder last year, online-born prescription-eyewear retailer Warby Parker is graduating to a second location in the state, this one in Denver. The new store opens Saturday in the Cherry Creek Shopping Center, 3000 E. First Ave. A third location is headed to Lower Downtown’s Dairy Block later this year, although a date has not been announced. Warby Parker started in 2010 exclusively as an e-commerce company, relying on in-house designers and direct sales to customers to keep the costs of its stylish frames and prescription eyeglasses and sunglasses lower than its brick-and-mortar competitors.