RGB Sensing

I have a project where the input will be from a RGB LED - it can be Green, Red or Blinking Red.

I need a quick and cheap sensor to read and differentiate between the three possible states. Is there a way to use a simple Photo cell (CdS photoresistor -http://www.adafruit.com/products/161 OR http://www.adafruit.com/products/1384) to differentiate between RGB?

I know i can use the RGB Color sensor but the project is quite cost sensitive for now. (http://www.adafruit.com/products/1334)

Thank

How about 2 or 3 ldrs connected to analog inputs?

http://www.ebay.co.uk/itm/5-x-Photodetector-Light-Dependent-Resistors-LDR-1k-25k-/271283863427?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item3f29c73f83

Put colour filters of some kind in front of them. Then a bit of experimentation to determine the levels detected by each ldr for each of the rgb led colours.

http://www.ebay.co.uk/itm/12-Colors-Gel-Filter-Kit-with-Velcro-for-Canon-Nikon-Sony-Minolta-Metz-Flash-/190865197387?pt=UK_CamerasPhoto_CameraAccessories_CameraFlashUnits_JN&hash=item2c7073c94b

You could use a paper hole punch to make small discs of the filter material and glue them to the ldrs.

This looks workable, any idea where I can get the color filters?

Sorry, just updated my reply!

Thanks, I am going to try this and get back to you