RS232 wire color - Electrical Engineering Stack Exchange RS232 (aka EIA232/TIA232) describes the electrical (voltage levels) and mechanical (connector type and pinout) aspect of the interface. Wire colors are not part of this, you can do with them whatever you want. Like David says, you can't even be sure that black is ground. RS232 TX, RX & GND wire colors? | Electronics Forum Aug 24, 2008As far as I know, there are no colour standards for wiring in regards to RS232 implementations, only pin assignments. A lot of people (including myself) wire DB9 connectors to mimic a guideline colour scheme used for RS232 on RJ45 (EIA-561).