I want to use 3 leds for a color sensor with the arduino. I saw the page: http://www.arduino.cc/playground/Learning/LEDSensor Where it talks about how to wire it up. My question, would it be more accurate to use red, green and blue colored leds for light sensing as opposed to photo resistors with colored filters?
I really doubt it. LED's are very poor converters of light to current. There are dedicated photodiodes which are a bit more expensive than LED's, but are specially designed to convert light to current.
Special "color sensing" modules are available with built in red, green, and blue color filters. Look at the Taos TCS230 for example. It's about $4 but it does exactly that. Maybe a bit more expensive than photoresistors with filters, but it's a 1-part solution!
I found that using a clear package LED of the red type gave the best results. This is because a red LED will respond to all colours with a shorter wavelength than red where as a green one will only respond to wavelengths shorter than green.
While light sensing with LEDs is not ideal it does work. Take a look at my page:- http://www.thebox.myzen.co.uk/Workshop/LED_Sensing.html