I create a set of documents that have charts build using the highcharts library. I'm not sure what is happening, but all of a sudden it seems that switch from version 7 to version 8 of prince has caused a problem with the size and colour of the spark line.
I attached an image with the html and pdf view side by side.
I attached an image with the html and pdf view side by side.

Presumably you are not running the JavaScript in Prince, as Prince 7 did not support JavaScript.