Hi @xliu,
I don't know what is the variable behind the color shown in your Graph, but try using this variable in the "Overlay" panel.
Using the "Add Line" it will connect the individual dots of each color (example here with BigFamily dataset with age as Overlay variable) :
You can provide an anonymised dataset if you would like to have guidance on your dataset.
Hope this will help you
Victor GUILLER
Data & Analytics