Using your natural brow colour shade is your best choice.
Dark-haired ladies though, should not use a shade that’s too dark. If you have very dark hair, use a dark brown shade for a more realistic look.
If your brows are fair, choose a pencil two shades darker than your hair.
Please note: NEVER EVER fill in your brows with black pencil
Read https://jagabeauty.wordpress.com/2013/11/15/me-and-my-bestie-my-angle-brush-n-i/ for more on getting the perfect brow shape.