Now I begin to lighten/shade the heart. Remember, if you're working digitally, never use black and white to shade/highlight. To give a drawing variation, you need to give it many colors. In the world we see this is apparent; if you look at a leaf outside you'd say it's green, but i'd tell you that's wrong. Light and darkness give objects different tonal values, so a green leaf is not always particularly green. Our eyes absorb the color of what we see, and unless it's a plain color before us, an object cannot be 'just one color'.