Observable Plot allows variable fills for an area or line, as inthis example.

This example would translate to SveltePlot as:

<Plotcolor={{type:'log',legend:true }}>    <AreaYdata={aapl}x="Date"y="Close"fill="Volume"z="null" />    <RuleYdata={[0]} /></Plot>

However, this currently renders with a single color:

(This is one of the issues surfaced by#72)