They’ve made their lists and checked them twice! ­Retailers are ready to shop at JCK. Here’s what they’ll be bringing back from Mandalay Bay.Rose gold, yellow gold, colored gems, and sliced diamonds and stones are topping to-buy lists of retailers heading to JCK Las Vegas, coming to the Mandalay Bay Resort & Casino from May 31 through June 3. Jewelers in cities from Seattle to Atlanta enjoyed a robust holiday season in 2012 and are reporting solid initial returns for the first quarter of 2013. As a result, buyers appear confident for the remainder of the year and many say they are planning to maintain or increase inventory.Colored gems were extremely successful last year at many stores—and most owners don’t anticipate a slowdown in the months to come. “Color is very strong so I think we’ll be looking for a lot of it,” says Marni Mulvey, a sales professional and buyer