Apple will add a gold color option for its full-size iPads in an effort to boost a category that’s posted declining shipments this year, according to people familiar with the plans. New versions of the company’s 9.7-inch iPads, anticipated to be unveiled this month, will include gold as a choice of color for the rear metal cover, adding to the silver and gray available for the lighter iPad Air, the people said, asking not to be identified ahead of an announcement. That brings the color palette into line with the iPhone 5s, which come with silver or gold backs for models with a white faceplate, and space gray for those with a black front. Teresa Brewer, a spokeswoman for Cupertino, California-based Apple, declined to comment. Sales of the iPad have declined for the past two quarters after soaring from $5 billion when the product was introduced in 2010 to $30 billion in 2012. Last year, iPad sales produced $32 billion.