I am trying to build a robot that detects cubes of a certain color, and later picks them up.

I was planning to use a camera and process the image, but I was told that Arduino is not capable of image processing.

Now, I was thinking that I could maybe use a photoresistor that is enclosed by a green light filter sheet (so that only the light of a certain color can pass). Thus, if my robot is facing a cube of the color I want, the photoresistor should detect this.

Is this at all possible? I know how filters work in theory, but I have never used one before.

If not, is there another way to try to detect color using an Arduino?