> For the complete documentation index, see [llms.txt](https://learn.arduinosa.co.za/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://learn.arduinosa.co.za/sensor-kits/37-in-1-sensor-kit/two-color-3mm.md).

# Two Color 3mm

![](https://451694785-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MPda5vaSVRKTQ6AoAmb%2Fuploads%2Fgit-blob-cd39f5b17e012e15b74160ee13d86694bf1b55ba%2Fimage.png?alt=media)

The 3mm bi-color LED has a common cathode (- pin), connected with the ‘-’ pin on the PCB. The centre pin activates the red light and the ‘S’ pin the green light. No series resistor is included in the circuit. A suitable value for low voltage operation would be 220 ohms.