Adafruit bi colour redgreen led displays with i2c backpack kit adafruit 1721 the adafruit bi colour bargraph backpack kit uses a clever constant current driver chip to take all the pain out of driving its 48 leds you just have to supply an i2c bus from your microcontroller each segment contains 1 x red led and 1 x green led giving you 4 x states red green yellow and off each led can be set to one of 16 x brightness levels as well normally this would require a mass of wiring and gpi