If you add a lot of Urad Dal to the batter, Dosas will turn dark brown. The lentils are often used to get the crispy texture and golden brown color to the Dosas and similar dishes. As for the taste, it will have a bit of impact on the taste as well.  When you increase the quantity of lentils in the batter, they usually lend an earthy taste to the palate. Quick Tip: If you have added more lentils to the batter, don't make Plain Dosas.  Instead, it would be perfect for making a Vegetable Uttapam or Pizza Dosa or traditional Masala Dosa. These additions will somewhat help in toning down the effect of lentils in your Dosa.