Yes, you can, but why would you????/ Everything that makes for a good tattoo takes contrast, that is why they are usually outlined in black. Without the black outline the color wouldn't look as crisp and sharp.
The only way your brown outine with brown shading would look good would be if you used a really dark brown outline with a lighter brown shading....And you know what the bummer would be? Brown is a color noted for its ability to lose color in the skin.....So think before you act...Tatubaron