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.

We’ve seen similar projects, but we are always struck how simple this sensor is to use. Combine these with an RGB LED and you can make a chameleon.

Off the shelf RGB colour pickers allowing you to extract and objects RGB values can range from a few hundred dollars to thousands depending on your needs.