Legacy 1/4in. ColorConnex Industrial Type D FNPT Coupler. ColorConnex is a patented system that uses color matching of couplers. By using ColorConnex to dedicate line use, you can ensure you never use a lubricated line for a dry line application, preventing cross contamination. Plugs among the standard pneumatic interchanges. Match coupler and plug types. Dedicate hose applications. Type: Type D (Industrial). Thread: 1/4 in. FNPT. Made from Steel/Aluminum.