You can get a spare cable for the Sony MDR-7506 headphones, which should last a looong time!
Or, this is a generic copy, cheaper but should be perfect for what you need:
Amazon.com: Geekria Audio Cable Replacement for Sony MDR-7506 7509 V6 V600 V700 V900 Headphones Coiled Repair Cable/Spring Replacement Cord (45Inch, Black): Home Audio & Theater
www.amazon.com
See the review on that listing for the wire colours.
(If you want to get complete new headphones, consider the MDR-7506; they are exceptional quality, virtually indestructible and even come with a spare parts list for maintenance...)