also, where is this data coming from? In addition, I'm sure better contrasting colors can be picked.
They're using highcharts.js, and it is quite the type of headache that is usually a pain to solve in highcharts in a not-very-hackish way... (and a good reason to learn enough D3.js to do a simple 3-item sparkline plot)
I'm pretty sure there is a setting on highcharts to treat missing data points as zero. They just have to set that to false, not too complicated...?
Quite likely there's an option for this scenario (since it's incredibly common), but sometimes there isn't one, or what you want is not implemented/interesting/useful for other use cases... And then pain follows.
can you take a screenshot to show us what you're talking about?