Google has lots of answers:
TSC230 Color Sensor Demo For Arduino:
http://www.elecfreaks.com/1666.html
Sensing color with the ADJD-S311 + Arduino
http://bildr.org/2012/01/adjd-s311_arduino/
Sensing color with the ADJD-S371 + Arduino
http://bildr.org/2011/01/adjd-s371-tutorial/