Draw XXL documentation

public ChartLine AddLine(string name, Color color = default(Color), bool newLineRepresentsBoolValues = false)

If the premade lines are not sufficient then you can use this function to add more lines manually, as described in more detail here.
The advantage of this function over just using the AddValue() overload that also creates a new line is that you get a reference to the newly created line back as return value. You can then use the returned line to customize it, e.g. with another color, or title,width, or xy or yz,... (todo<-auf all die Beispiele hier am Satzende dann wohl verlinken...)

The color parameter:
If left as default then the new line automatically gets a color assigned that is as different as possible compared to the already existing lines.

The newLineRepresentsBoolValues parameter:
Disables some unused minimum/maximum apex visualization to make the line more readable.