Algodoo

Why are you setting the color to [1,1,1,1] anyways? If you leave the color manipulations out, the stuff wont get bleached ^^

Visual indications ;=;

Ah, I see. You could use a different kind of visual indication for that, for example spawning small "particles", like circles, or only changing the color of the hammer side. Changing the color of affected stuff should be accompanied with a way of returning the color, for example by manipulating their poststep on collision temporarily, however that requires some use of the eval function, which is a little too complex for you I believe ^^