Description ColorConnex Color Code System allows for easy, color-to-color matching of couplers and plugs among pneumatic interchanges. It also solves the problem of potential crossing and contaminating of different air lines. As air line interchanges became popular in the automotive industry, different manufacturers developed their own styles in an attempt to capture the market. As a result, various incompatible, yet nearly identical-looking types emerged. To be able to recognize each type, one would have to memorize the bands on all the coupler sleeves and the shapes of all plugs. Now, with ColorConnex, the Type D 1/4 in. Industrial Series is easily identified by its red color!