Each time I make a new custom-graph I am surprised by a new set of colours.
I have not figured out which system/mechanism is the base of the colour-selection.
That variation of colours makes it (more) difficult to explain the contents of such graphs to other people.
Is it not easier to attach a 'fixed' colour to a selected input in the righthand sidebar?
In that way the custom graphs can be better compared, because then always the same colour for the same input.
Requires some thinking if more than 1 value from that input should be shown, but

To be clear: I do not ask for a user-selectable colour for a specific parameter.
That would be nice-to-have, but a standard fixed combination is a good basic solution.