A PC fan's wire colors are pretty consistent, with red almost invariably marking the positive and black marking the negative or ground. The third wire varies depending on the manufacturer, but usually, it is blue or yellow. You don't need it to make the fan turn, but the third wire is there for a good reason. Color Codes for a 3-Wire Computer Fan | Techwalla Was this helpful? Color Codes for a 3-Wire Computer Fan | Techwalla Nov 28, 20183-Pin Fan Connector. Running a low-voltage fan requires only two wires: one for the positive or "hot" lead and one for the negative or ground. A PC fan's wire colors are pretty consistent, with red almost invariably marking the positive and black marking the negative or ground.Author: Fred Decker Motherboard (CPU) 3 Pin Fan Connector · AllPinouts 3 Pin Fan connector used on the ATX Motherboard. 3 PIN IDC FEMALE at the fan and 3 PIN IDC MALE header at the motherboard. Not all fans or motherboards control or power the fan assemblies the same way. Fans may be either 5 Volt DC or 12 Volt DC fans. Colors may change. Chassis and CPU fans may use either 3-pin or 4-pin power connectors.