Hi Lucas
The Story Map Shortlist app doesn't support different color points in the same tab by design.
A legend can be added via customization but I couldn't find an example of a Shortlist with that added. Some authors have added legends to the Story Map Tour via customization: Gallery | Story Maps
Another approach that we sometimes see used in the Map Tour which you could use in Shortlist is to use the header to present text/graphics to serve as a legend, for example
http://urbanobservatory.maps.arcgis.com/apps/MapTour/index.html?appid=fa5b66adb57b4205a38731c45a6cb2...
http://usfs.maps.arcgis.com/apps/MapTour/index.html?appid=3dfab0794d5e4f0f886590da8765f4f5
Have you seen The Story Map Playlist app? It supports multiple colors and also has a built-in legend, so it might be a good one to use: http://storymaps.arcgis.com/en/app-list/playlist/
Note: There's also a Story Maps Space on Geonet. I recommend posting on there for help with developing with and customizing the Esri Story Maps apps: /community/gis/web-gis/storymaps/content
Rupert
Story Maps team
