NSMB.com:

Here is a how to guide on changing normal black cables or hose on your bike to pretty much any color you could want. Not only is black boring, but the hard coating on the outside of the cables can rub through paint and even aluminum. I have seen a Hayes brake cable eat right through the stanchion on a Fox 40. Braided stainless brake lines look nice, but are expensive running over $50 a line and don’t match your derailleur cable. By using the same heat shrink tubing electricians use you can protect your frame and match your cables to any color scheme for your bike.

[Jenni, This one’s got you written all over it…]
Source: Blue Collar Mountain Biking