This particular recipe creates a biscuit that is light in color, so the overall color does not change much from the dough. However, you can see the cracks in the crust and gently touch the biscuit to judge doneness. It shouldn't be sticky (at all), and resist your touch a bit. I do insert a toothpick in the center to make sure the middle is done, but 15 minutes in a 400ºF oven is the best bet that you will have a fully-baked product.