Sparkfun's FTDI cable is constructed around an FT232RQ, which is encased in a USB A connector. The opposite end of the cable terminates with a 2.54mm pitch, 6-pin connector featuring the following pinout: RTS, RX, TX, 5V, CTS, GND. The green cable is the RTS, and the black cable is the GND.
The FTDI cable shares similar pinout and functionality with Sparkfun's FTDI Basic Breakout board, making it suitable for programming Arduino Pro, Pro Mini, and Lilypad, among others. When using with these boards, match the black and green wires of the FTDI cable with the 'BLK' and 'GRN' labels on the PCB. Despite the cable having a 5V Vcc compared to the breakout's 3.3V Vcc, it will not damage these Arduino circuit boards.
Originally intended to have a 3.3V VCC, a miscommunication with the supplier resulted in a batch of FTDI cables with a 5V VCC and 3.3V I/O. While the 5V Vcc output shouldn't pose an issue, it might be unsuitable for powering sensitive circuits like sensors.
The FTDI Cable and the FTDI Basic each have their advantages and disadvantages. The FTDI Basic possesses excellent LED indicators but requires a Mini-B cable. In contrast, the FTDI Cable is well-protected against the elements but is larger and less easily embeddable into a project. The FTDI Basic utilizes DTR for a hardware reset, while the FTDI cable uses the RTS signal.