Color Issues in History

I’ve seen this for a while now on my HASS installation, but now I’ve run out of ideas on how to tackle it, maybe somebody can help me here:
The history information was displayed nicely colored in the beginning (started mid December’16), but lately, a lot of my charts looks like this:

There’s a lot of white on white :confused:

Is there a way to reset these color choices / settings anywhere?
Haven’t found anything re. this topic anywhere.

The only way I got this resolved was a complete new installation.