Currently in the contact dashboard if DNC in ON it will show an "V" check-mark by the phone number and the phone number will be red
If DNC is OFF it will show an "X" icon by the phone number
The "V" and "X" are the buttons to change the DNC status but they maybe confusing as the X may lead to believe that DNC is enabled.
Very confusing, X means you can call the number and a check mark means you can't very backwards to what most people viewing it thinks.