Usually I'm use Blue theme and all good with it. But nearly I'm try to use Dark theme and get bad expirience with graph.

This is graph in Blue theme:

This is same graph in Dark theme:

As can you see both graphs have working time delimiters, but in dark theme it is tear out the eye.

I'm try to investigate and fix this problem by editing CSS file, but this not hava effect... 

Color of work-off time is #ebebeb which is founded in ".timeline-axis" class in CSS, but when I'm change it to another color graph still displayed with #ebebeb for work-off time.