He used an Arduino, and multiplexed RGB LEDs with some digital potentiometers ... By entering the correct color code, the pad will flash green and unlock the door for 10 seconds.

Messing around with Arduino can lead to some fun projects ... due to possible variance in the manufacturing process. These color bands and the necessary orientation to read them are universal ...

Neopixels, or WS2812Bs, are addressable RGB LEDs , which can be controlled individually by a microcontroller, in this case, an Arduino ... to recall the visible color spectrum or the rainbow ...

If you’d like to get more specific, Michael Klements’ Arduino-based scanner lets you quantify colors in numerical RGB values via a TCS34725 sensor. User interface for the handheld device is ...