The first thing to understand is that no standardization exists between manufacturers. Colors of the wires are coded, and are specific to each wire's function. For a battery's wiring, red is usually positive, and green or black is usually ground or negative. The colors in a wiper motor wire may stand for something completely different. For example, green may be designated as the positive lead of a wiper motor. You cannot interchange colors codes from one manufacturer to the next, since each has their own "in-house" color scheme.
To understand the manufacturer's color code on the wires, a wiring diagram (sometimes called a schematic) is almost a necessity. By tracing down what the diagram color states, you will be able to figure out the color codes. Reading a diagram requires a good knowledge base of electrical design. If you feel additional expertise is needed, seek out the assistance of a qualified auto electrician, who can decipher the diagram for you.
Testing the internal integrity of the motor is difficult through the wires, since internal circuitry may block electrical flow. If you attempt to read the coils by using an ohmmeter, the resistance given may not be the true resistance of the motor when it is running. This is because the internal circuitry may have current sensing switches. When no current is present, solid state switches turn off, indicating an open reading when, in fact, the motor is in good condition.