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.

Description: In this project I did a Christmas jumper with rgb LEDs, this can also be a creative clothing project or whatever ...

Posted in Arduino Hacks, LED Hacks Tagged arduino, HL1606, led, lighting, lightstrip, rgb, serial, synaptic labs ← IPhone 3.0 Tethering Is Easy Meat Thermometer Using Predictive Filtering → ...

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.

For prototyping, Infineon has a RGB LED lighting control shield for Arduino, based around its ARM Cortex-M0 XMC1202 microcontroller. On board is something called a ‘brightness colour control unit’ ...