This is a good Techno Finger Tip that makes this green heart turn pink before your very eyes. But the heart itself doesn't change colour at all - it's just an optical illusion. You can try it for yourself by drawing a heart on a white background in any computer paint program. Many such programs already have a heart as a pre-selectable shape. Fill it with a green colour. For the colour change to work, you have to stare at the heart for about thirty seconds, and then delete it, so that you're left with just a plain white screen. As you stare, the colour receptors in your eyes become less and less sensitive to green, the only colour they can see in the image you're looking at. Instead they become more and more sensitive to a pinky red colour, which is the opposite of green. When the heart disappears, you should see a floating after image of the heart in the correct colours! Why not have a go with some of these? Just click the one you want and it will load up in a new window. Press start, get staring and after thirty seconds the image will disappear, leaving you with the a floating after image in the correct colours! Skull and Crossbones Bottle Of Blood Flower Heart If you like the idea, why not adapt it? When sending a Valentine in February, why not make up a card on white paper with a green heart on the front. Remember to tell the person you're sending it to that they should look at the green heart for about thirty seconds before flipping it over to the plain white back, so that they get the illusion.