how to protect outdoor cables
Paint

All the answers posted so far entail shielding devices which themselves will require paint to last very long under UV light bombardment.  So with or without them, you will need a suitable primer and paint.  

I recommend running a Scotchbrite pad down the wire or shield before priming, to give the material some microscopic "tooth" for the primer to lock into.  Then a solvent based primer.   Then an exterior rated paint of your choice. 

If you want to match what you have on the house, find a way to remove something that is painted in that color, and the hardware store can match it with their scanner.