It could be Fathom Blue original paint. Could be.
From the exterior colors section I grabbed this paragraph. By the time that car was built, Fathom Blue was not a standard color.
In 1968, two colors, Tuxedo Black and Cordovan Maroon, started the year common to both Camaro and Corvette. In January 1968, three additional Corvette colors were added to Camaro, with specific marketing attention given to the fact that they were Corvette colors applied to Camaro. These three were Corvette Bronze, LeMans Blue, and British Green. (In addition to these three, Rallye Green was another mid-season Camaro color addition. Together they replaced Fathom Blue, Grecian Green, Palomino Ivory, and Tuxedo Black for the remainder of 1968.) As a result, Corvette shared a total of five colors with Camaro in 1968.