The irony in the making of this cartoon, is that dogs can indeed see in colour, but not within the red and green spectrums. In fact, dogs can see yellow, grey and blue – this is equivalent to the human red-green colour blindness. Dogs only possess two colour receptors (commonly called cones), whereas humans have three, allowing them to see a broader spectrum of colours.
What can we learn for this? Well for one thing, you might be better off buying yellow or blue coloured toys rather than red or green, making it easier for the dog to distinguish it from the green grass.
Why not test the theory and throw two toys simultaneously – one blue/yellow, the other red/green – See if there is a preference.