In general, the current official rules and game updates tell you what you can and cannot use for competitions in FLL:
In the series of pictures in Rule 4 of the official rules (page 18), it provides pictures of the allowed sensors.
The allowed light sensor is third from the left
<Picture (Device Independent Bitmap) 1.jpg>
The allowed color sensor is fifth from the left
<Picture (Device Independent Bitmap) 2.jpg>
Technically, the optical sensor which comes with the current educational kit is the "light sensor" which can detect differences in ambient and reflected light (using its red LED). When used to detect reflected light, the light sensor can detect differences in both black and white and different colors, but it can only determine the intensity of the reflected light (almost like "grey scale"). This sensor is essentially color-blind and its purpose does not include the ability to distinguish between different colors (e.g. blue vs. red). The light sensor can be calibrated to adjust to the light levels expected during the sensor's operation.
The color sensor is available either by separate purchase (using the link you cited) or when you purchase the Version 2.0 "retail kit". The color sensor can distinguish between different colors of light (distinguishing among six colors) in addition to what the light sensor can detect. Also, if desired, it can be used as a color lamp, emitting red, green, or blue light. Assuming you are using NXT-G to program your robot, your team would need to use the latest version of the software (LEGO® MINDSTORMS® Education NXT Software 2.1). The color sensor cannot be currently calibrated. For a little sensor trivia, the although the color sensor appears to have three devices on its front end, only two of the three are actually used. The third is just a feature to look pretty.
Have Fun (Core Value #8) and Good Luck!
From: First Lego League in Virginia and DC [mailto:[log in to unmask]
] On Behalf Of Parakh Saini Batra
Sent: Wednesday, October 10, 2012 4:41 PM
To: [log in to unmask]
Subject: EXT :[VADCFLL-L] color sensor
Rookie coach here…I am a little confused about the color sensor. The one that came with the educational kit is a light sensor and can distinguish between light and dark (black & white) ---correct?
...and the color sensor I am finding online is:
If I am not mistaken this is not an official Lego part and is not legal for use in the competition?
I appreciate any clarification I can get on this! :) Kind regards, -Parakh