Contact the seller first.
My experience is that you should use the magic words Not As Described.
That should earn you a return with full refund, including your original shipping and a free ship back. Some sellers won't want to be charged with this offense and may just refund your total purchase and tell you to keep or donate the item.
If you need to open a return with eBay/Paypal, (because seller is stubborn or wants to argue with you) doesn't hurt to take a picture(s) of the item in good daylight showing the true color and upload that with your return request to eBay, where it indicates you can.
ETA: some listings will say the seller doesn't accept returns. Doesn't matter. This is deceptive and you'll get your money back anyway.
