Abstract: A keying system, especially for use with intermateable electrical connector assemblies is disclosed. An electrical connector assembly includes first and second interconnectable electrical connectors. The first connector includes a first keying means formed into a raised pattern of letters identifying a particular color. The mating second connector is colored the particular color and includes a pattern of cavities corresponding to the pattern of letters. The second connector accommodates the first connector in singular unique orientation, with the color of the second connector easily visually identifying the mateability of the first connector thereto.