I am making a wedding cake this weekend. One layer needs to be blue. The couple is announcing that they are having a boy. Besides just tinting the cake blue what could I do to flavor the cake a flavor that is blue that will go with chocolate?

I would use blueberry.

... or a Blue Velvet cake. It's the same flavor as Red Velvet but tinted blue.

... or blue raspberry

I would ask the couple if they would like a particular flavor. They may prefer a vanilla cake with blue color.