Some great news from HiTechnic.
They've got a color sensor in the works - I've edited the description just a bit, but here's all the details:
The HiTechnic NXT Compatible Color Sensor works by illuminating the target surface with three colored light sources (Light Emitting Diodes or LEDs), one red, one green and one blue. The difference between ambient illumination and the increase due to each light source output is used to measure the target surface’s adsorption for each color. The three color values are further processed to correct for the spread of each LED’s spectral output.
Three values are returned to the NXT: RED level, GREEN level, and BLUE level. Each color level is returned as a value between 0 – 255. For example, if values returned were Red = 255, Green = 255, Blue = 0, the target color is Yellow.
The sensor updates the color data at a rate of 100 samples per second.
The HiTechnic Color Sensor has a mode control feature permitting two types of calibration function to be performed by the NXT program.
Black level calibration may be used to null unwanted reflected light from the structure in which the sensor has been placed.
White balance calibration may be used to balance the sensitivity of the sensor for each of the three LED outputs when illuminating a white target at a specified distance.
The mode control defaults to 0, normal measurement mode.
If mode control is set to 1, the sensor will operate in white balance cal. mode and will expect to be pointed at a diffuse white surface at a distance of ~15mm. When the cal. function has finished, the LEDs will blink and the mode will automatically reset to 0, normal measurement mode. The cal. process takes about ¼ second. Calibration data is stored in non-volatile memory and will be retrieved each time power is applied to the sensor.
If mode control is set to 2, the sensor will operate in black level cal. mode and will expect to be pointed into empty space with no objects within a 90º cone for a distance of at least 0.5m. Black level cal. measures the signal for each color and creates an offset to null the ambient level for all future measurements. When the cal. function has finished, the LEDs will blink and the mode will automatically reset to 0, normal measurement mode. The cal. process takes about 1 second. Black level cal. may be used to offset signals being returned from parts of the surrounding structure. Calibration data is stored in non-volatile memory and will be retrieved each time power is applied to the sensor.
According to HiTechnic, they are VERY BUSY and have a LOT of things planned for us... please be sure to visit their site over the next few days when they make some official announcements.