Currently, graphs are defined in terms of graph color. This means that
when the system palette is changed, the old colors are still used. We
switch to storing the color roles and looking up the palette colors on
paint events. We also define the graph line background color as the
graph color at half-transparency.
Now that WindowServer broadcasts the system theme using an anonymous
file, we need clients to pledge "recvfd" so they can receive it.
Some programs keep the "shared_buffer" pledge since it's still used for
a handful of things.
