Take a look at a dog\'s claws. Look at how the claw is darker towards the toe, and lighter towards the end. Also notice the streaking. The basic colouring might be blended from dark to light, but the streaks are quite well defined. Go and take a look at the real thing, enlightment guaranteed.
And yep, what demonherald said, whatever you\'re painting, claws/teeth/horns, the method is the same, you only change the colours.