Using the tooltipServiceWrapper.ts example

Is there a way to modify the getTooltipData(value: any): VisualTooltipDataItem[] 

{
displayName:  value,
value: 
header: " " ,
color: 

}

This is working perfect with multiple instances for what I need , I am using a function for the color.  But I would like to change the default Bullet of a Circle to be able to change it to match the symbol on our chart. 

I am new to this PowerBI and tscript.. So I might be missing something.  

Kathy