Why doesn't a stripped/cracked MagSafe power cable shock?

Behold, the fate of all (poorly handled) MagSafe power cables:

Why doesn't this shock me? I've read that MagSafe cables are low voltage, but I don't even get a tingle. Is there any danger of shock, arcing, and/or fire from a MagSafe cable in this condition? If so, is a strip of electrical tape over the exposed wire a sufficient 'fix'?

Bonus question: what is the source of the green and yellow discoloration?

Magsafe cables only carry voltages ranging from 14.5 to 20 volts, which is not nearly enough to be able to feel. For more information, see this Electrical Engineering Stack Exchange question. You would not be able to touch the actual conductors anyways as the metal "wire" that is visible in this picture does not carry any current, as it is just shielding around smaller insulated wires. It is unlikely for arcing to occur, but you should still get the charger replaced soon. Like iPhone and iPad chargers, always buy MagSafe chargers from an Apple Store or the Apple website as ones bought on eBay and Amazon are known to be non-UL listed counterfeits.

The accepted answer is incorrect.

The outer wire sheath carries V-, connected to the outermost MagSafe pins. It's also connected to the inner metal part of the MagSafe connector, the part that snaps with the magnet. All of these were verified with a multimeter.

When connected, it connects with the MacBook's ground system (checked with a multimeter). There's continuity between that metal sheath and GND, such as the outer metal part of a USB connector.

It's wrapped around an inner wire, which carries V+. Presumably, that's to help reduce RF emissions.

Why aren't you shocked? Most probably, your body simply doesn't make a good electrical path.

I also cannot feel a shock when sitting on an office chair. However, I do feel a tingle when leaning against something earthed, like a concrete wall. It gets stronger the harder I lean against said wall, which reduces resistance to earth.