It turns out that most plain white electrical cords are actually covered in normal, everyday PVC, and that means you can make them any colour you want with a bit of PVC cleaner and the right coloured solvent dye.
Not all cords are wrapped in PVC, but a majority of them are. The best way to find out is to dab a bit of purple PVC primer on the cord (available at any most local hardware stores) to see if it takes. If it does, then you can decide on the right colour you want to dye that bland, white cord. Of course, if purple is your thing, then you can just get down with your purple primer.
If purple isn't your first choice, almost any colour can be mixed using PVC cleaner (also available at the hardware store) and the solvent dye of your choice. So if you've got some boring white cords lying around, check out the full instructions for this quick little project over at Make: Online, and be sure to wear gloves!
Make: Projects – Cable Dyeing [Make: Online]