I've had some experience with how the color palette for graphs are created and how they'll be used. It goes something like this:

Manager (to engineer): We need sexier looking reports. Get some design help.

Engineer (to designer): I can't change the graph type, but can you pick out some colors that look better?

Designer: <winces at the current box of crayons color palette> Sure, here are 8 colors that go well together, and can actually be found in nature.

The problem is, it's not just 8 or 16 colors. There are a few use cases:

1. A chart that shows activity levels versus a warning or critical threshold. The color of the activity lines should be something not green, yellow or red. Those colors typically are used for the threshold value. We might put 12 metrics on a single time-series chart, so we needed 12 colors. If you get over 12, the time-series is a mess anyway.

2. A chart that has several less related metrics. Traffic = dark blue, CPU = dark brown, Memory = dark purple. Again, a max of 12 colors.  In many, but not all cases, we would put different metrics on different charts, so the same color can be reused.

3. A chart that compares two values, like inbound and outbound traffic on the same link. We might plot two links on the same chart, four lines total, so we'd like the paired attributes to use related colors.  Link 1 inbound = light blue, link 1 outbound = dark blue, link 2 inbound = light brown, link 2 outbound = dark brown.

4. Sometimes our charts have three stats for a single metric, like minimum, average, and maximum CPU utilization. We wanted three related colors.  We'd plot a maximum of 3 metrics, 3 stats each, needing 9 colors total... three shades of blue, three shades of brown, three shades of purple.

5. Our reports are sometimes projected on large screens in network operation centers (NOCs), and customers have asked for the graphs on a black background. Any palette we created that worked well on white had several colors that didn't work well on black. I suggest creating a second palette for use on black.

I'm not trying to suggest colors, just how some of the colors in the palette should be related to each other. Our final result was to pick four basic colors with three variations each.

Possibly, instead of using related colors, you could specify when to use dashed lines or other patterns to achieve the above.