I had a look on familysearch.org, but couldn't find a single person with that surname. I did find quite a few with the surname Colomy, so maybe it was changed?
I did find a burial notice for a Katherine Colomy Dziekanowicz ( Katherine is the English spelling of Katarzyna ), but it is probably not the right one, plus I'm slightly uncertain as to the relationship between Jan and the Kolomyi family. Did he marry one of them?
Do you have any further information other than what you have given?