I was having an argument with ChatGPT today, initially about Bi-Colour LEDs, then it spilled over to Tri-Colour LEDs.

Let me explain. A Bi-Colour LED has two different colour LEDs in the one package. In theory any two colours could be used but Red & Green or Red & Yellow are pretty common.

Now according to ChatGPT, a Bi-Colour LED has 3 pins. Assuming it is a Common Cathode LED, then there is one Cathode Pin (negative), and two Anode pins (positive). The internal LED Cathodes are connected together and the internal LED Anode pins are each connected to an external pin. This makes it possible to illuminate either of the internal LEDs; hence Bi-Colour. However, it’s also possible to illuminate both LEDs giving a new output colour. So isn’t this really a Tri-Colour LED ?

When I asked ChatGPT about this, it decided that a Tri-Colour LED has 3 internal LEDs; typically Red, Blue & Green, making it an RGB LED.

You can also have a Bi-Colour LED with only two pins. Connect the LED one way and you get one colour from the LED, reverse it’s connections you get a different colour. It’s only possible for one of the internal LEDs to be illuminated at any time; though you can quickly alternate between the two thus giving a 3 colour effect.

I’m not sure what the “official” answer is, but I have, and probably always will categorise LEDs as follows:

A Bi-Colour LED has two internal LED chips of different colours, two external pins and produces two different colours depending on which way around it’s pins are connected.

A Tri-Colour LED also has two internal LED chips of different colours but has three external pins. Either the internal LEDs Anodes or Cathodes are connected together to form a common pin, meaning it’s possible to light either one or both the internal LEDs thus producing one, two or three colours.

An RGB LED has three internal LED chips; Red, Green and Blue. Either the three LED Anodes or Cathodes are commoned together and connected to an external pin, and the other pins of the internal LEDs are each connected to their own external pin. These LEDs have four external pins and are capable of producing seven different colours not including different shades by varying the brightness of one or more of the internal LEDs.

There are of course mono colour LEDs; or just LEDs, flashing LEDs, rainbow effect LEDs, flickering LEDs and heavens knows what other types.