One of the Arduino projects that everyone should try is the coloured lolly sorter, and you can't build one of these without a colour sensor. The Colour Sensor Module can give individual greyscale, red, green and blue colour levels with just three IO pins, and features bright white LEDs for even illumination.

Features:

 - Mounting holes for easy project building

 - Can be set to read red, green, blue or greyscale levels

 - Very fast response times with PWM output

 - Optimal detection distance 1cm