The jeans you show should be fine - especially on casual night. Black jeans do look a little dressier than blue-jeans. Blue denim jeans just look sloppy, it is not just the color, it is the drape. Jeans tend to wrinkle and cling to the body. Slacks drape down and have a crease.
It looks to me that "nice" jeans are allowed on casual nights - but they are not recommended on "formal suggested" nights. On those nights people should stick with slacks.
The key on casual nights is that the jeans should be new and stylish - not frayed, worn-out or bad fitting. And guys - PLEASE wear a belt - (we don't want to see the tops of any butt-cracks peeking out while we eat dinner).