[9fans] alg to make a good colour palette for a graph

[George Michaelson <ggm@apnic.net>]

totally non Plan9 question but people here oftentimes have nice simple algs
which work well across lots of contexts.

I need to make a set of <n> visually distinctive colours in rgb space such
that I can feed the rgb values into a tool (RRD) to graph with.

Microsloth picks colours for you. a very nasty muted set. Gnuplot repeats the
same palette of colours over and over again.

I read in the RRD list of a technique to map the <n> as equidistant points
distributed in HSV space, and then use them. But, no code.

N varies. Usually its less than 15. In those cases I think I can use an
Acronymic 'Richard Of York Gave Battle In Vain' selection. But for one case I
am looking at, I need 250+ reasonably distinctive colours.

I thought about just taking a 256colourmap, and randomizing it, and using the
entire palette that way. It should mean no two adjacent colours are very alike
which is fine for a stacked line chart.

Is there something simple and nice, which I can do in AWK? Something which
will go into the ff-space and pick good colour combos? The obvious things I
come up with make gray (for a stunningly obvious reason) It would be super
nice to have up to 25 or 30 colours which are all mutually equi-distant in
some sense.

clues? I've tried web browsing. its phenominal how few things seem remotely
relevant from keyword searches using colourspace, colourmap, palette, graph.

-George