Owen Evans writes:
The June 2017 release of Story Map Cascade has a new dark theme and font options for the titles and body text in your story. These options are available in the Story Map Cascade Builder for anyone to use.
In addition, it is now possible to do additional customizations, by editing parameters in a Cascade story JSON, to go beyond what the new options in the Cascade Builder allow you to do. For example you can make further modifications to the overall graphic theme of a Cascade, and to choose from a wide range of fonts.
Read the blog post...