CQRobot TCS34725FN Color Sensor Compatible with Raspberry Pi/Arduino/STM32. ADC, I2C Interface, Output RGB Data/Light Intensity Table. for Light Test, Phones, Computers, Industries, Lighting.

This device plugs in easily to your Raspberry Pi use the wiki guide linked on the amazon page as there are no included instructions. There are sample programs on the WIKI page is very useful the Python code requires you to have pygame, smbus (plus time and math) to be installed to run the python library. It is very flexible as to what it is capable of reading: RGB data, Lux, colour temp. The code is fully ready to run out of the box and can be adapted easily to your own needs.

Very well made but lacks any really helpful instructions so we were lucky we already knew what to do. Bargain but know your stuff first.

Got this to measure colour with an arduino. Needs to be quite close to subject unless you're trying to make a colour temperature meter. Arduino code downloadable from link in listing and then adaptable for your purpose. I'm still working on translating the figures it gives into figures that make sense to me - i.e.: RGB values in Photoshop; but I'm sure that just a bit more tinkering.

Excellent quality and value for money. Instantly connects to devices and holds signal/communication well. Seems well made and set to last.