Your comments

It seems I used names of properties incorrectly... This works as expected:
TrackerFormatString = "{0}\nTime: {2:yyyy-MM-dd HH:mm}\nValue: {4:0.0000}";
What format string do I need to format DateTime like "yyyy-MM-dd HH:mm"?

For example for line series of DataPoint I code
TrackerFormatString = "{0}\nTime: {X:???}\nValue: {Y:0.0000}";
X - time axis
Is there any progress on this feature?
I faced the task to collapse weekends on DateTimeAxis to avoid gaps in graphs. Maybe there are some solutions.
It would be handy to customize such scale breaks. E.g. from Friday 20:00 to Monday 8:00 (for excluding weekends) or from 0:00 to 8:00 (for exluding nights).

Nick, thank you!

Yes, I can set series color in code and it won't be changed. I think if we let an user to show and hide series we should keep their colors.

In order to get the default behaviour it's also necessary to set a series linestyle.

My solution
int _currentColorIndex;
List<OxyColor> LineColors { get; set; }
ourLineSeries.LineStyle = (LineStyle)((_currentColorIndex / LineColors.Count) % (int)LineStyle.None);
ourLineSeries.Color = LineColors[_currentColorIndex++ % LineColors.Count];
Is it possible to get access to default color collection?