What difference can a little headspace on your secondary make?

https://hoard.nidavellir.net/media/oxysmall.jpg

These two carboys of pear wine were poured from the same primary! Look at that color difference! Which one do you think caused this color change? Is it the headspace? Was it because I poured the darker one last? These have been sitting about a month now. 

 Might be the headspace oxidising it when it was racked. At the same time perhaps some of the tannin settled to the bottom of the juice so the container that was poured last came out darker!? Its an interesting question.