I am always intrigued by how Patina ultimately develops on leather. It is always different with every item and the development is never the same. These are the things that makes vegetable-taned leather so wonderful to work with and have.
Being a big fan of vegetable-tanned leather, iL Bisonte has always been one of my favorite leather goods brand. Their leather is the most beautiful I have ever seen, with quality by far the most superior. I was on their website a few days ago and found a cool short video illustrating how Patina develops on leather. The video shows the gradual color change on one of iL Bisonte's wallet. It first presents the wallet when it is still new and light in color, then gradually changing into a deeper Patina with the dirt and usage marks also present on it.
If you have not fallen in love with vegetable-tanned leather yet, this short video should. You can check out the video on the iL Bisonte website here.