I had some analysis (Line chart), at which there are values which is < 30, and it is good that there is an indicator of different color or marker for values < 30 and values > 30, which this indicator, my users would be able to distinct out what what to focus , what not to.
Chun, there is a possible workaround as documented here:
https://community.tibco.com/wiki/visualize-data-line-chart-where-line-color-varies-using-scatter-plot-line-connections