You can throw a Raspberry Pi camera and OpenCV at the problem and approach it through software, or you can buy an off-the-shelf RGB sensor and wire it up to an Arduino.

Here is a simple, yet useful circuit of an Arduino 4-digit 7-segment LED display unit. The module used here is a self-contained, compact common-cathode module containing four 7-segment LED numeric ...

The Arduino-compatible lighting RGB LED lighting shield reviewed here was designed to give designers a low-cost easy-to-use open-source platform for fast prototyping and inexpensive evaluation of ...