Item Not As Described (Dispute)

Hello,

 

Sorry for posting this again but I can find my original post.

 

I have a buyer that says I shipped him the wrong colour phone, however when I checked all my communications and the order details, he didn't specify the colour. He has now opened an eBay dispute. Should I let him escalate the case to eBay or should I just swallow it up and send him a refund?

 

I know for a fact he didn't specify colour. What is the best course of action?