By default, 1st coating should be gray and second is the final coat which is the required color. Here's the reference in case you are provided with Federal Standard paint in the instruction,
Federal Standard 595 Fed-Std-595 Color Specification, Fan Deck, Paint Chips
Some modeling paint like the Italeri, Revell, Pactra included the FS standards unlike Tamiya. Nice thing in tamiya is you're going to mix in order to have the exact color matching.